skin care thesis topics

• Research article
• Open access
• Published: 12 June 2019

The impact of skin care products on skin chemistry and microbiome dynamics

• Amina Bouslimani 1   na1 ,
• Ricardo da Silva 1   na1 ,
• Tomasz Kosciolek 2 ,
• Stefan Janssen 2 , 3 ,
• Chris Callewaert 2 , 4 ,
• Amnon Amir 2 ,
• Kathleen Dorrestein 1 ,
• Alexey V. Melnik 1 ,
• Livia S. Zaramela 2 ,
• Ji-Nu Kim 2 ,
• Gregory Humphrey 2 ,
• Tara Schwartz 2 ,
• Karenina Sanders 2 ,
• Caitriona Brennan 2 ,
• Tal Luzzatto-Knaan 1 ,
• Gail Ackermann 2 ,
• Daniel McDonald 2 ,
• Karsten Zengler 2 , 5 , 6 ,
• Rob Knight 2 , 5 , 6 , 7 &
• Pieter C. Dorrestein 1 , 2 , 5 , 8  

BMC Biology volume  17 , Article number:  47 ( 2019 ) Cite this article

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Use of skin personal care products on a regular basis is nearly ubiquitous, but their effects on molecular and microbial diversity of the skin are unknown. We evaluated the impact of four beauty products (a facial lotion, a moisturizer, a foot powder, and a deodorant) on 11 volunteers over 9 weeks.

Mass spectrometry and 16S rRNA inventories of the skin revealed decreases in chemical as well as in bacterial and archaeal diversity on halting deodorant use. Specific compounds from beauty products used before the study remain detectable with half-lives of 0.5–1.9 weeks. The deodorant and foot powder increased molecular, bacterial, and archaeal diversity, while arm and face lotions had little effect on bacterial and archaeal but increased chemical diversity. Personal care product effects last for weeks and produce highly individualized responses, including alterations in steroid and pheromone levels and in bacterial and archaeal ecosystem structure and dynamics.

Conclusions

These findings may lead to next-generation precision beauty products and therapies for skin disorders.

The human skin is the most exposed organ to the external environment and represents the first line of defense against external chemical and microbial threats. It harbors a microbial habitat that is person-specific and varies considerably across the body surface [ 1 , 2 , 3 , 4 ]. Recent findings suggested an association between the use of antiperspirants or make-up and skin microbiota composition [ 5 , 6 , 7 ]. However, these studies were performed for a short period (7–10 days) and/or without washing out the volunteers original personal care products, leading to incomplete evaluation of microbial alterations because the process of skin turnover takes 21–28 days [ 5 , 6 , 7 , 8 , 9 ]. It is well-established that without intervention, most adult human microbiomes, skin or other microbiomes, remain stable compared to the differences between individuals [ 3 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ].

Although the skin microbiome is stable for years [ 10 ], little is known about the molecules that reside on the skin surface or how skin care products influence this chemistry [ 17 , 18 ]. Mass spectrometry can be used to detect host molecules, personalized lifestyles including diet, medications, and personal care products [ 18 , 19 ]. However, although the impact of short-term dietary interventions on the gut microbiome has been assessed [ 20 , 21 ], no study has yet tested how susceptible the skin chemistry and Microbiome are to alterations in the subjects’ personal care product routine.

In our recent metabolomic/microbiome 3D cartography study [ 18 ], we observed altered microbial communities where specific skin care products were present. Therefore, we hypothesized that these products might shape specific skin microbial communities by changing their chemical environment. Some beauty product ingredients likely promote or inhibit the growth of specific bacteria: for example, lipid components of moisturizers could provide nutrients and promote the growth of lipophilic bacteria such as Staphylococcus and Propionibacterium [ 18 , 22 , 23 ]. Understanding both temporal variations of the skin microbiome and chemistry is crucial for testing whether alterations in personal habits can influence the human skin ecosystem and, perhaps, host health. To evaluate these variations, we used a multi-omics approach integrating metabolomics and microbiome data from skin samples of 11 healthy human individuals. Here, we show that many compounds from beauty products persist on the skin for weeks following their use, suggesting a long-term contribution to the chemical environment where skin microbes live. Metabolomics analysis reveals temporal trends correlated to discontinuing and resuming the use of beauty products and characteristic of variations in molecular composition of the skin. Although highly personalized, as seen with the microbiome, the chemistry, including hormones and pheromones such as androstenone and androsterone, were dramatically altered. Similarly, by experimentally manipulating the personal care regime of participants, bacterial and molecular diversity and structure are altered, particularly for the armpits and feet. Interestingly, a high person-to-person molecular and bacterial variability is maintained over time even though personal care regimes were modified in exactly the same way for all participants.

Skin care and hygiene products persist on the skin

Systematic strategies to influence both the skin chemistry and microbiome have not yet been investigated. The outermost layer of the skin turns over every 3 to 4 weeks [ 8 , 9 ]. How the microbiome and chemistry are influenced by altering personal care and how long the chemicals of personal care products persist on the skin are essentially uncharacterized. In this study, we collected samples from skin of 12 healthy individuals—six males and six females—over 9 weeks. One female volunteer had withdrawn due to skin irritations that developed, and therefore, we describe the remaining 11 volunteers. Samples were collected from each arm, armpit, foot, and face, including both the right and left sides of the body (Fig.  1 a). All participants were asked to adhere to the same daily personal care routine during the first 6 weeks of this study (Fig.  1 b). The volunteers were asked to refrain from using any personal care product for weeks 1–3 except a mild body wash (Fig.  1 b). During weeks 4–6, in addition to the body wash, participants were asked to apply selected commercial skin care products at specific body parts: a moisturizer on the arm, a sunscreen on the face, an antiperspirant on the armpits, and a soothing powder on the foot (Fig.  1 b). To monitor adherence of participants to the study protocol, molecular features found in the antiperspirant, facial lotion, moisturizer, and foot powder were directly tracked with mass spectrometry from the skin samples. For all participants, the mass spectrometry data revealed the accumulation of specific beauty product ingredients during weeks 4–6 (Additional file  1 : Figure S1A-I, Fig.  2 a orange arrows). Examples of compounds that were highly abundant during T4–T6 in skin samples are avobenzone (Additional file  1 : Figure S1A), dexpanthenol (Additional file  1 : Figure S1B), and benzalkonium chloride (Additional file  1 : Figure S1C) from the facial sunscreen; trehalose 6-phosphate (Additional file  1 : Figure S1D) and glycerol stearate (Additional file  1 : Figure S1E) from the moisturizer applied on arms; indolin (Additional file  1 : Figure S1F) and an unannotated compound ( m/z 233.9, rt 183.29 s) (Additional file  1 : Figure S1G) from the foot powder; and decapropylene glycol (Additional file  1 : Figure S1H) and nonapropylene glycol (Additional file  1 : Figure S1I) from the antiperspirant. These results suggest that there is likely a compliance of all individuals to study requirements and even if all participants confirmed using each product every day, the amount of product applied by each individual may vary. Finally, for weeks 7–9, the participants were asked to return to their normal routine by using the same personal care products they used prior to the study. In total, excluding all blanks and personal care products themselves, we analyzed 2192 skin samples for both metabolomics and microbiome analyses.

Study design and representation of changes in personal care regime over the course of 9 weeks. a Six males and six females were recruited and sampled using swabs on two locations from each body part (face, armpits, front forearms, and between toes) on the right and left side. The locations sampled were the face—upper cheek bone and lower jaw, armpit—upper and lower area, arm—front of elbow (antecubitis) and forearm (antebrachium), and feet—in between the first and second toe and third and fourth toe. Volunteers were asked to follow specific instructions for the use of skin care products. b Following the use of their personal skin care products (brown circles), all volunteers used only the same head to toe shampoo during the first 3 weeks (week 1–week 3) and no other beauty product was applied (solid blue circle). The following 3 weeks (week 4–week 6), four selected commercial beauty products were applied daily by all volunteers on the specific body part (deodorant antiperspirant for the armpits, soothing foot powder for the feet between toes, sunscreen for the face, and moisturizer for the front forearm) (triangles) and continued to use the same shampoo. During the last 3 weeks (week 7–week 9), all volunteers went back to their normal routine and used their personal beauty products (circles). Samples were collected once a week (from day 0 to day 68—10 timepoints from T0 to T9) for volunteers 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, and 12, and on day 0 and day 6 for volunteer 8, who withdraw from the study after day 6. For 3 individuals (volunteers 4, 9, 10), samples were collected twice a week (19 timepoints total). Samples collected for 11 volunteers during 10 timepoints: 11 volunteers × 10 timepoints × 4 samples × 4 body sites = 1760. Samples collected from 3 selected volunteers during 9 additional timepoints: 3 volunteers × 9 timepoints × 4 samples × 4 body sites = 432. See also the “ Subject recruitment and sample collection ” section in the “ Methods ” section

Monitoring the persistence of personal care product ingredients in the armpits over a 9-week period. a Heatmap representation of the most abundant molecular features detected in the armpits of all individuals during the four phases (0: initial, 1–3: no beauty products, 4–6: common products, and 7–9: personal products). Green color in the heatmap represents the highest molecular abundance and blue color the lowest one. Orange boxes with plain lines represent enlargement of cluster of molecules that persist on the armpits of volunteer 1 ( b ) and volunteer 3 ( c , d ). Orange clusters with dotted lines represent same clusters of molecules found on the armpits of other volunteers. Orange arrows represent the cluster of compounds characteristic of the antiperspirant used during T4–T6. b Polyethylene glycol (PEG) molecular clusters that persist on the armpits of individual 1. The molecular subnetwork, representing molecular families [ 24 ], is part of a molecular network ( http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=f5325c3b278a46b29e8860ec5791d5ad ) generated from MS/MS data collected from the armpits of volunteer 1 (T0–T3) MSV000081582 and MS/MS data collected from the deodorant used by volunteer 1 before the study started (T0) MSV000081580. c , d Polypropylene glycol (PPG) molecular families that persist on the armpits of individual 3, along with the corresponding molecular subnetwork that is part of the molecular network accessible here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=aaa1af68099d4c1a87e9a09f398fe253 . Subnetworks were generated from MS/MS data collected from the armpits of volunteer 3 (T0–T3) MSV000081582 and MS/MS data collected from the deodorant used by volunteer 3 at T0 MSV000081580. The network nodes were annotated with colors. Nodes represent MS/MS spectra found in armpit samples of individual 1 collected during T0, T1, T2, and T3 and in personal deodorant used by individual 1 (orange nodes); armpit samples of individual 1 collected during T0, T2, and T3 and personal deodorant used by individual 1 (green nodes); armpit samples of individual 3 collected during T0, T1, T2, and T3 and in personal deodorant used by individual 3 (red nodes); armpit samples of individual 3 collected during T0 and in personal deodorant used by individual 3 (blue nodes); and armpit samples of individual 3 collected during T0 and T2 and in personal deodorant used by individual 3 (purple nodes). Gray nodes represent everything else. Error bars represent standard error of the mean calculated at each timepoint from four armpit samples collected from the right and left side of each individual separately. See also Additional file  1 : Figure S1

To understand how long beauty products persist on the skin, we monitored compounds found in deodorants used by two volunteers—female 1 and female 3—before the study (T0), over the first 3 weeks (T1–T3) (Fig.  1 b). During this phase, all participants used exclusively the same body wash during showering, making it easier to track ingredients of their personal care products. The data in the first 3 weeks (T1–T3) revealed that many ingredients of deodorants used on armpits (Fig.  2 a) persist on the skin during this time and were still detected during the first 3 weeks or at least during the first week following the last day of use. Each of the compounds detected in the armpits of individuals exhibited its own unique half-life. For example, the polyethylene glycol (PEG)-derived compounds m/z 344.227, rt 143 s (Fig.  2 b, S1J); m/z 432.279, rt 158 s (Fig.  2 b, S1K); and m/z 388.253, rt 151 s (Fig.  2 b, S1L) detected on armpits of volunteer 1 have a calculated half-life of 0.5 weeks (Additional file  1 : Figure S1J-L, all p values < 1.81e−07), while polypropylene glycol (PPG)-derived molecules m/z 481.87, rt 501 s (Fig.  2 c, S1M); m/z 560.420, rt 538 s (Fig.  2 c, S1N); m/z 788.608, rt 459 s (Fig.  2 d, S1O); m/z 846.650, rt 473 s (Fig.  2 d, S1P); and m/z 444.338, rt 486 s (Fig.  2 d, S1Q) found on armpits of volunteers 3 and 1 (Fig.  2 a) have a calculated half-life ranging from 0.7 to 1.9 weeks (Additional file  1 : Figure S1M-Q, all p values < 0.02), even though they originate from the same deodorant used by each individual. For some ingredients of deodorant used by volunteer 3 on time 0 (Additional file  1 : Figure S1M, N), a decline was observed during the first week, then little to no traces of these ingredients were detected during weeks 4–6 (T4–T6), then finally these ingredients reappear again during the last 3 weeks of personal product use (T7–T9). This suggests that these ingredients are present exclusively in the personal deodorant used by volunteer 3 before the study. Because a similar deodorant (Additional file  1 : Figure S1O-Q) and a face lotion (Additional file  1 : Figure S1R) was used by volunteer 3 and volunteer 2, respectively, prior to the study, there was no decline or absence of their ingredients during weeks 4–6 (T4–T6).

Polyethylene glycol compounds (Additional file  1 : Figure S1J-L) wash out faster from the skin than polypropylene glycol (Additional file  1 : Figure S1M-Q)(HL ~ 0.5 weeks vs ~ 1.9 weeks) and faster than fatty acids used in lotions (HL ~ 1.2 weeks) (Additional file  1 : Figure S1R), consistent with their hydrophilic (PEG) and hydrophobic properties (PPG and fatty acids) [ 25 , 26 ]. This difference in hydrophobicity is also reflected in the retention time as detected by mass spectrometry. Following the linear decrease of two PPG compounds from T0 to T1, they accumulated noticeably during weeks 2 and 3 (Additional file  1 : Figure S1M, N). This accumulation might be due to other sources of PPG such as the body wash used during this period or the clothes worn by person 3. Although PPG compounds were not listed in the ingredient list of the shampoo, we manually inspected the LC-MS data collected from this product and confirmed the absence of PPG compounds in the shampoo. The data suggest that this trend is characteristic of accumulation of PPG from additional sources. These could be clothes, beds, or sheets, in agreement with the observation of these molecules found in human habitats [ 27 ] but also in the public GNPS mass spectrometry dataset MSV000079274 that investigated the chemicals from dust collected from 1053 mattresses of children.

Temporal molecular and bacterial diversity in response to personal care use

To assess the effect of discontinuing and resuming the use of skin care products on molecular and microbiota dynamics, we first evaluated their temporal diversity. Skin sites varied markedly in their initial level (T0) of molecular and bacterial diversity, with higher molecular diversity at all sites for female participants compared to males (Fig.  3 a, b, Wilcoxon rank-sum-WR test, p values ranging from 0.01 to 0.0001, from foot to arm) and higher bacterial diversity in face (WR test, p  = 0.0009) and armpits (WR test, p  = 0.002) for females (Fig.  3 c, d). Temporal diversity was similar across the right and left sides of each body site of all individuals (WR test, molecular diversity: all p values > 0.05; bacterial diversity: all p values > 0.20). The data show that refraining from using beauty products (T1–T3) leads to a significant decrease in molecular diversity at all sites (Fig.  3 a, b, WR test, face: p  = 8.29e−07, arm: p  = 7.08e−09, armpit: p  = 1.13e−05, foot: p  = 0.002) and bacterial diversity mainly in armpits (WR test, p  = 0.03) and feet (WR test, p  = 0.04) (Fig.  3 c, d). While molecular diversity declined (Fig.  3 a, b) for arms and face, bacterial diversity (Fig.  3 c, d) was less affected in the face and arms when participants did not use skin care products (T1–T3). The molecular diversity remained stable in the arms and face of female participants during common beauty products use (T4–T6) to immediately increase as soon as the volunteers went back to their normal routines (T7–T9) (WR test, p  = 0.006 for the arms and face)(Fig.  3 a, b). A higher molecular (Additional file  1 : Figure S2A) and community (Additional file  1 : Figure S2B) diversity was observed for armpits and feet of all individuals during the use of antiperspirant and foot powder (T4–T6) (WR test, molecular diversity: armpit p  = 8.9e−33, foot p  = 1.03e−11; bacterial diversity: armpit p  = 2.14e−28, foot p  = 1.26e−11), followed by a molecular and bacterial diversity decrease in the armpits when their regular personal beauty product use was resumed (T7–T9) (bacterial diversity: WR test, p  = 4.780e−21, molecular diversity: WR test, p  = 2.159e−21). Overall, our data show that refraining from using beauty products leads to lower molecular and bacterial diversity, while resuming the use increases their diversity. Distinct variations between male and female molecular and community richness were perceived at distinct body parts (Fig.  3 a–d). Although the chemical diversity of personal beauty products does not explain these variations (Additional file  1 : Figure S2C), differences observed between males and females may be attributed to many environmental and lifestyle factors including different original skin care and different frequency of use of beauty products (Additional file  2 : Table S1), washing routines, and diet.

Molecular and bacterial diversity over a 9-week period, comparing samples based on their molecular (UPLC-Q-TOF-MS) or bacterial (16S rRNA amplicon) profiles. Molecular and bacterial diversity using the Shannon index was calculated from samples collected from each body part at each timepoint, separately for female ( n  = 5) and male ( n  = 6) individuals. Error bars represent standard error of the mean calculated at each timepoint, from up to four samples collected from the right and left side of each body part, of females ( n  = 5) and males ( n  = 6) separately. a , b Molecular alpha diversity measured using the Shannon index from five females (left panel) and six males (right panel), over 9 weeks, from four distinct body parts (armpits, face, arms, feet). c , d Bacterial alpha diversity measured using the Shannon index, from skin samples collected from five female (left panel) and six male individuals (right panel), over 9 weeks, from four distinct body parts (armpits, face, arms, feet). See also Additional file  1 : Figure S2

Longitudinal variation of skin metabolomics signatures

To gain insights into temporal metabolomics variation associated with beauty product use, chemical inventories collected over 9 weeks were subjected to multivariate analysis using the widely used Bray–Curtis dissimilarity metric (Fig.  4 a–c, S3A). Throughout the 9-week period, distinct molecular signatures were associated to each specific body site: arm, armpit, face, and foot (Additional file  1 : Figure S3A, Adonis test, p  < 0.001, R 2 0.12391). Mass spectrometric signatures displayed distinct individual trends at each specific body site (arm, armpit, face, and foot) over time, supported by their distinct locations in PCoA (principal coordinate analysis) space (Fig.  4 a, b) and based on the Bray–Curtis distances between molecular profiles (Additional file  1 : Figure S3B, WR test, all p values < 0.0001 from T0 through T9). This suggests a high molecular inter-individual variability over time despite similar changes in personal care routines. Significant differences in molecular patterns associated to ceasing (T1–T3) (Fig.  4 b, Additional file 1 : Figure S3C, WR test, T0 vs T1–T3 p  < 0.001) and resuming the use of common beauty products (T4–T6) (Additional file  1 : Figure S3C) were observed in the arm, face, and foot (Fig.  4 b), although the armpit exhibited the most pronounced changes (Fig.  4 b, Additional file 1 : Figure S3D, E, random forest highlighting that 100% of samples from each phase were correctly predicted). Therefore, we focused our analysis on this region. Molecular changes were noticeable starting the first week (T1) of discontinuing beauty product use. As shown for armpits in Fig.  4 c, these changes at the chemical level are specific to each individual, possibly due to the extremely personalized lifestyles before the study and match their original use of deodorant. Based on the initial use of underarm products (T0) (Additional file  2 : Table S1), two groups of participants can be distinguished: a group of five volunteers who used stick deodorant as evidenced by the mass spectrometry data and another group of volunteers where we found few or no traces suggesting they never or infrequently used stick deodorants (Additional file  2 : Table S1). Based on this criterion, the chemical trends shown in Fig.  4 c highlight that individuals who used stick deodorant before the beginning of the study (volunteers 1, 2, 3, 9, and 12) displayed a more pronounced shift in their armpits’ chemistries as soon as they stopped using deodorant (T1–T3), compared to individuals who had low detectable levels of stick deodorant use (volunteers 4, 6, 7, and 10), or “rarely-to-never” (volunteers 5 and 11) use stick deodorants as confirmed by the volunteers (Additional file  1 : Figure S3F, WR test, T0 vs T1–T3 all p values < 0.0001, with greater distance for the group of volunteers 1, 2, 3, 9, and 12, compared to volunteers 4, 5, 6, 7, 10, and 11). The most drastic shift in chemical profiles was observed during the transition period, when all participants applied the common antiperspirant on a daily basis (T4–T6) (Additional file  1 : Figure S3D, E). Finally, the molecular profiles became gradually more similar to those collected before the experiment (T0) as soon as the participants resumed using their personal beauty products (T7–T9) (Additional file  1 : Figure S3C), although traces of skin care products did last through the entire T7–T9 period in people who do not routinely apply these products (Fig.  4 c).

Individualized influence of beauty product application on skin metabolomics profiles over time. a Multivariate statistical analysis (principal coordinate analysis (PCoA)) comparing mass spectrometry data collected over 9 weeks from the skin of 11 individuals, all body parts, combined (first plot from the left) and then displayed separately (arm, armpits, face, feet). Color scale represents volunteer ID. The PCoA was calculated on all samples together, and subsets of the data are shown in this shared space and the other panels. b The molecular profiles collected over 9 weeks from all body parts, combined then separately (arm, armpits, face, feet). c Representative molecular profiles collected over 9 weeks from armpits of 11 individuals (volunteers 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12). Color gradient in b and c represents timepoints (time 0 to time 9), ranging from the lightest orange color to the darkest one that represent the earliest (time 0) to the latest (time 9) timepoint, respectively. 0.5 timepoints represent additional timepoints where three selected volunteers were samples (volunteers 4, 9, and 10). PCoA plots were generated using the Bray–Curtis dissimilarity matrix and visualized in Emperor [ 28 ]. See also Additional file  1 : Figure S3

Comparing chemistries detected in armpits at the end timepoints—when no products were used (T3) and during product use (T6)—revealed distinct molecular signatures characteristic of each phase (random forest highlighting that 100% of samples from each group were correctly predicted, see Additional file  1 : Figure S3D, E). Because volunteers used the same antiperspirant during T4–T6, molecular profiles converged during that time despite individual patterns at T3 (Fig.  4 b, c, Additional file  1 : Figure S3D). These distinct chemical patterns reflect the significant impact of beauty products on skin molecular composition. Although these differences may in part be driven by beauty product ingredients detected on the skin (Additional file  1 : Figure S1), we anticipated that additional host- and microbe-derived molecules may also be involved in these molecular changes.

To characterize the chemistries that vary over time, we used molecular networking, a MS visualization approach that evaluates the relationship between MS/MS spectra and compares them to reference MS/MS spectral libraries of known compounds [ 29 , 30 ]. We recently showed that molecular networking can successfully organize large-scale mass spectrometry data collected from the human skin surface [ 18 , 19 ]. Briefly, molecular networking uses the MScluster algorithm [ 31 ] to merge all identical spectra and then compares and aligns all unique pairs of MS/MS spectra based on their similarities where 1.0 indicates a perfect match. Similarities between MS/MS spectra are calculated using a similarity score, and are interpreted as molecular families [ 19 , 24 , 32 , 33 , 34 ]. Here, we used this method to compare and characterize chemistries found in armpits, arms, face, and foot of 11 participants. Based on MS/MS spectral similarities, chemistries highlighted through molecular networking (Additional file  1 : Figure S4A) were associated with each body region with 8% of spectra found exclusively in the arms, 12% in the face, 14% in the armpits, and 2% in the foot, while 18% of the nodes were shared between all four body parts and the rest of spectra were shared between two body sites or more (Additional file  1 : Figure S4B). Greater spectral similarities were highlighted between armpits, face, and arm (12%) followed by the arm and face (9%) (Additional file  1 : Figure S4B).

Molecules were annotated with Global Natural Products Social Molecular Networking (GNPS) libraries [ 29 ], using accurate parent mass and MS/MS fragmentation patterns, according to level 2 or 3 of annotation defined by the 2007 metabolomics standards initiative [ 35 ]. Through annotations, molecular networking revealed that many compounds derived from steroids (Fig.  5 a–d), bile acids (Additional file  1 : Figure S5A-D), and acylcarnitines (Additional file  1 : Figure S5E-F) were exclusively detected in the armpits. Using authentic standards, the identity of some pheromones and bile acids were validated to a level 1 identification with matched retention times (Additional file  1 : Figure S6B, S7A, C, D). Other steroids and bile acids were either annotated using standards with identical MS/MS spectra but slightly different retention times (Additional file  1 : Figure S6A) or annotated with MS/MS spectra match with reference MS/MS library spectra (Additional file  1 : Figure S6C, D, S7B, S6E-G). These compounds were therefore classified as level 3 [ 35 ]. Acylcarnitines were annotated to a family of possible acylcarnitines (we therefore classify as level 3), as the positions of double bonds or cis vs trans configurations are unknown (Additional file  1 : Figure S8A, B).

Underarm steroids and their longitudinal abundance. a – d Steroid molecular families in the armpits and their relative abundance over a 9-week period. Molecular networking was applied to characterize chemistries from the skin of 11 healthy individuals. The full network is shown in Additional file  1 : Figure S4A, and networking parameters can be found here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=284fc383e4c44c4db48912f01905f9c5 for MS/MS datasets MSV000081582. Each node represents a consensus of a minimum of 3 identical MS/MS spectra. Yellow nodes represent MS/MS spectra detected in armpits samples. Hexagonal shape represents MS/MS spectra match between skin samples and chemical standards. Plots are representative of the relative abundance of each compound over time, calculated separately from LC-MS1 data collected from the armpits of each individual. Steroids detected in armpits are a , dehydroisoandrosterone sulfate ( m/z 369.190, rt 247 s), b androsterone sulfate ( m/z 371.189, rt 261 s), c 1-dehydroandrostenedione ( m/z 285.185, rt 273 s), and d dehydroandrosterone ( m/z 289.216, rt 303 s). Relative abundance over time of each steroid compound is represented. Error bars represent the standard error of the mean calculated at each timepoint from four armpit samples from the right and left side of each individual separately. See also Additional file  1 : Figures S4-S8

Among the steroid compounds, several molecular families were characterized: androsterone (Fig.  5 a, b, d), androstadienedione (Fig.  5 c), androstanedione (Additional file  1 : Figure S6E), androstanolone (Additional file  1 : Figure S6F), and androstenedione (Additional file  1 : Figure S6G). While some steroids were detected in the armpits of several individuals, such as dehydroisoandrosterone sulfate ( m/z 369.19, rt 247 s) (9 individuals) (Fig.  5 a, Additional file  1 : Figure S6A), androsterone sulfate ( m/z 371.189, rt 261 s) (9 individuals) (Fig.  5 b, Additional file  1 : Figure S6C), and 5-alpha-androstane-3,17-dione ( m/z 271.205, rt 249 s) (9 individuals) (Additional file  1 : Figure S6E), other steroids including 1-dehydroandrostenedione ( m/z 285.185, rt 273 s) (Fig.  5 c, Additional file  1 : Figure S6B), dehydroandrosterone ( m/z 289.216, rt 303 s) (Fig.  5 d, Additional file 1 : Figure S6D), and 5-alpha-androstan-17.beta-ol-3-one ( m/z 291.231, rt 318 s) (Additional file  1 : Figure S6F) were only found in the armpits of volunteer 11 and 4-androstene-3,17-dione ( m/z 287.200, rt 293 s) in the armpits of volunteer 11 and volunteer 5, both are male that never applied stick deodorants (Additional file  1 : Figure S6G). Each molecular species exhibited a unique pattern over the 9-week period. The abundance of dehydroisoandrosterone sulfate (Fig.  5 a, WR test, p  < 0.01 for 7 individuals) and dehydroandrosterone (Fig.  5 a, WR test, p  = 0.00025) significantly increased during the use of antiperspirant (T4–T6), while androsterone sulfate (Fig.  5 b) and 5-alpha-androstane-3,17-dione (Additional file  1 : Figure S6E) display little variation over time. Unlike dehydroisoandrosterone sulfate (Fig.  5 a) and dehydroandrosterone (Fig.  5 d), steroids including 1-dehydroandrostenedione (Fig.  5 c, WR test, p  = 0.00024) and 4-androstene-3,17-dione (Additional file  1 : Figure S6G, WR test, p  = 0.00012) decreased in abundance during the 3 weeks of antiperspirant application (T4–T6) in armpits of male 11, and their abundance increased again when resuming the use of his normal skin care routines (T7–T9). Interestingly, even within the same individual 11, steroids were differently impacted by antiperspirant use as seen for 1-dehydroandrostenedione that decreased in abundance during T4–T6 (Fig.  5 c, WR test, p  = 0.00024), while dehydroandrosterone increased in abundance (Fig.  5 d, WR test, p  = 0.00025), and this increase was maintained during the last 3 weeks of the study (T7–T9).

In addition to steroids, many bile acids (Additional file  1 : Figure S5A-D) and acylcarnitines (Additional file  1 : Figure S5E-F) were detected on the skin of several individuals through the 9-week period. Unlike taurocholic acid found only on the face (Additional file  1 : Figures S5A, S7A) and tauroursodeoxycholic acid detected in both armpits and arm samples (Additional file  1 : Figures S5B, S7B), other primary bile acids such as glycocholic (Additional file  1 : Figures S5C, S7C) and chenodeoxyglycocholic acid (Additional file  1 : Figures S5D, S7D) were exclusively detected in the armpits. Similarly, acylcarnitines were also found either exclusively in the armpits (hexadecanoyl carnitines) (Additional file  1 : Figures S5E, S8A) or in the armpits and face (tetradecenoyl carnitine) (Additional file  1 : Figures S5F, S8B) and, just like the bile acids, they were also stably detected during the whole 9-week period.

Bacterial communities and their variation over time

Having demonstrated the impact of beauty products on the chemical makeup of the skin, we next tested the extent to which skin microbes are affected by personal care products. We assessed temporal variation of bacterial communities detected on the skin of healthy individuals by evaluating dissimilarities of bacterial collections over time using unweighted UniFrac distance [ 36 ] and community variation at each body site in association to beauty product use [ 3 , 15 , 37 ]. Unweighted metrics are used for beta diversity calculations because we are primarily concerned with changes in community membership rather than relative abundance. The reason for this is that skin microbiomes can fluctuate dramatically in relative abundance on shorter timescales than that assessed here. Longitudinal variations were revealed for the armpits (Fig.  6 a) and feet microbiome by their overall trend in the PCoA plots (Fig.  6 b), while the arm (Fig.  6 c) and face (Fig.  6 d) displayed relatively stable bacterial profiles over time. As shown in Fig.  6 a–d, although the microbiome was site-specific, it varied more between individuals and this inter-individual variability was maintained over time despite same changes in personal care routine (WR test, all p values at all timepoints < 0.05, T5 p  = 0.07), in agreement with previous findings that individual differences in the microbiome are large and stable over time [ 3 , 4 , 10 , 37 ]. However, we show that shifts in the microbiome can be induced by changing hygiene routine and therefore skin chemistry. Changes associated with using beauty products (T4–T6) were more pronounced for the armpits (Fig.  6 a, WR test, p  = 1.61e−52) and feet (Fig.  6 b, WR test, p  = 6.15e−09), while little variations were observed for the face (Fig.  6 d, WR test, p  = 1.402.e−83) and none for the arms (Fig.  6 c, WR test, p  = 0.296).

Longitudinal variation of skin bacterial communities in association with beauty product use. a - d Bacterial profiles collected from skin samples of 11 individuals, over 9 weeks, from four distinct body parts a) armpits, b) feet, c) arms and d) face, using multivariate statistical analysis (Principal Coordinates Analysis PCoA) and unweighted Unifrac metric. Each color represents bacterial samples collected from an individual. PCoA were calculated separately for each body part. e , f Representative Gram-negative (Gram -) bacteria collected from arms, armpits, face and feet of e) female and f) male participants. See also Additional file  1 : Figure S9A, B showing Gram-negative bacterial communities represented at the genus level

A significant increase in abundance of Gram-negative bacteria including the phyla Proteobacteria and Bacteroidetes was noticeable for the armpits and feet of both females (Fig.  6 e; Mann–Whitney U , p  = 8.458e−07) and males (Fig.  6 f; Mann–Whitney U , p  = 0.0004) during the use of antiperspirant (T4–T6), while their abundance remained stable for the arms and face during that time (Fig.  6 e, f; female arm p  = 0.231; female face p value = 0.475; male arm p = 0.523;male face p  = 6.848751e−07). These Gram-negative bacteria include Acinetobacter and Paracoccus genera that increased in abundance in both armpits and feet of females (Additional file  1 : Figure S9A), while a decrease in abundance of Enhydrobacter was observed in the armpits of males (Additional file  1 : Figure S9B). Cyanobacteria, potentially originating from plant material (Additional file  1 : Figure S9C) also increased during beauty product use (T4–T6) especially in males, in the armpits and face of females (Fig.  6 e) and males (Fig.  6 f). Interestingly, although chloroplast sequences (which group phylogenetically within the cyanobacteria [ 38 ]) were only found in the facial cream (Additional file  1 : Figure S9D), they were detected in other locations as well (Fig.  6 e, f. S9E, F), highlighting that the application of a product in one region will likely affect other regions of the body. For example, when showering, a face lotion will drip down along the body and may be detected on the feet. Indeed, not only did the plant material from the cream reveal this but also the shampoo used for the study for which molecular signatures were readily detected on the feet as well (Additional file  1 : Figure S10A). Minimal average changes were observed for Gram-positive organisms (Additional file  1 : Figure S10B, C), although in some individuals the variation was greater than others (Additional file  1 : Figure S10D, E) as discussed for specific Gram-positive taxa below.

At T0, the armpit’s microflora was dominated by Staphylococcus (26.24%, 25.11% of sequencing reads for females and 27.36% for males) and Corynebacterium genera (26.06%, 17.89% for females and 34.22% for males) (Fig.  7 a—first plot from left and Additional file  1 : Figure S10D, E). They are generally known as the dominant armpit microbiota and make up to 80% of the armpit microbiome [ 39 , 40 ]. When no deodorants were used (T1–T3), an overall increase in relative abundance of Staphylococcus (37.71%, 46.78% for females and 30.47% for males) and Corynebacterium (31.88%, 16.50% for females and 44.15% for males) genera was noticeable (WR test, p  < 3.071e−05) (Fig.  7 a—first plot from left), while the genera Anaerococcus and Peptoniphilus decreased in relative abundance (WR test, p  < 0.03644) (Fig.  7 a—first plot from left and Additional file  1 : Figure S10D, E). When volunteers started using antiperspirants (T4–T6), the relative abundance of Staphylococcus (37.71%, 46.78% females and 30.47% males, to 21.71%, 25.02% females and 19.25% males) and Corynebacterium (31.88%, 16.50% females and 44.15% males, to 15.83%, 10.76% females and 19.60% males) decreased (WR test, p  < 3.071e−05) (Fig.  7 a, Additional file  1 : Figure S10D, E) and at the same time, the overall alpha diversity increased significantly (WR test, p  = 3.47e−11) (Fig.  3 c, d). The microbiota Anaerococcus (WR test, p  = 0.0006018) , Peptoniphilus (WR test, p  = 0.008639), and Micrococcus (WR test, p  = 0.0377) increased significantly in relative abundance, together with a lot of additional low-abundant species that lead to an increase in Shannon alpha diversity (Fig.  3 c, d). When participants went back to normal personal care products (T7–T9), the underarm microbiome resembled the original underarm community of T0 (WR test, p  = 0.7274) (Fig.  7 a). Because armpit bacterial communities are person-specific (inter-individual variability: WR test, all p values at all timepoints < 0.05, besides T5 p n.s), variation in bacterial abundance upon antiperspirant use (T4–T6) differ between individuals and during the whole 9-week period (Fig.  7a —taxonomic plots per individual). For example, the underarm microbiome of male 5 exhibited a unique pattern, where Corynebacterium abundance decreased drastically during the use of antiperspirant (82.74 to 11.71%, WR test, p  = 3.518e−05) while in the armpits of female 9 a huge decrease in Staphylococcus abundance was observed (Fig.  7 a) (65.19 to 14.85%, WR test, p  = 0.000113). Unlike other participants, during T0–T3, the armpits of individual 11 were uniquely characterized by the dominance of a sequence that matched most closely to the Enhydrobacter genera . The transition to antiperspirant use (T4–T6) induces the absence of Enhydrobacter (30.77 to 0.48%, WR test, p  = 0.01528) along with an increase of Corynebacterium abundance (26.87 to 49.74%, WR test, p  = 0.1123) (Fig.  7 a—male 11).

Person-to-person bacterial variabilities over time in the armpits and feet. a Armpit microbiome changes when stopping personal care product use, then resuming. Armpit bacterial composition of the 11 volunteers combined, then separately, (female 1, female 2, female 3, male 4, male 5, male 6, male 7, female 9, male 10, male 11, female 12) according to the four periods within the experiment. b Feet bacterial variation over time of the 12 volunteers combined, then separately (female 1, female 2, female 3, male 4, male 5, male 6, male 7, female 9, male 10, male 11, female 12) according to the four periods within the experiment. See also Additional file  1 : Figure S9-S13

In addition to the armpits, a decline in abundance of Staphylococcus and Corynebacterium was perceived during the use of the foot powder (46.93% and 17.36%, respectively) compared to when no beauty product was used (58.35% and 22.99%, respectively) (WR test, p  = 9.653e−06 and p  = 0.02032, respectively), while the abundance of low-abundant foot bacteria significantly increased such as Micrococcus (WR test, p  = 1.552e−08), Anaerococcus (WR test, p  = 3.522e−13), Streptococcus (WR test, p  = 1.463e−06), Brevibacterium (WR test, p  = 6.561e−05), Moraxellaceae (WR test, p  = 0.0006719), and Acinetobacter (WR test, p  = 0.001487), leading to a greater bacterial diversity compared to other phases of the study (Fig.  7 b first plot from left, Additional file  1 : Figure S10D, E, Fig.  3 c, d).

We further evaluated the relationship between the two omics datasets by superimposing the principal coordinates calculated from metabolome and microbiome data (Procrustes analysis) (Additional file  1 : Figure S11) [ 34 , 41 , 42 ]. Metabolomics data were more correlated with patterns observed in microbiome data in individual 3 (Additional file  1 : Figure S11C, Mantel test, r  = 0.23, p  < 0.001), individual 5 (Additional file  1 : Figure S11E, r  = 0.42, p  < 0.001), individual 9 (Additional file  1 : Figure S11H, r  = 0.24, p  < 0.001), individual 10 (Additional file  1 : Figure S11I, r  = 0.38, p  < 0.001), and individual 11 (Additional file  1 : Figure S11J, r  = 0.35, p  < 0.001) when compared to other individuals 1, 2, 4, 6, 7, and 12 (Additional file  1 : Figure S11A, B, D, F, G, K, respectively) (Mantel test, all r  < 0.2, all p values < 0.002, for volunteer 2 p n.s). Furthermore, these correlations were individually affected by ceasing (T1–T3) or resuming the use of beauty products (T4–T6 and T7–T9) (Additional file  1 : Figure S11A-K).

Overall, metabolomics–microbiome correlations were consistent over time for the arms, face, and feet although alterations were observed in the arms of volunteers 7 (Additional file  1 : Figure S11G) and 10 (Additional file  1 : Figure S11I) and the face of volunteer 7 (Additional file  1 : Figure S11G) during product use (T4–T6). Molecular–bacterial correlations were mostly affected in the armpits during antiperspirant use (T4–T6), as seen for volunteers male 7 (Additional file  1 : Figure S11G) and 11 (Additional file  1 : Figure S11J) and females 2 (Additional file  1 : Figure S11B), 9 (Additional file  1 : Figure S11H), and 12 (Additional file  1 : Figure S11K). This perturbation either persisted during the last 3 weeks (Additional file  1 : Figure S11D, E, H, I, K) when individuals went back to their normal routine (T7–T9) or resembled the initial molecular–microbial correlation observed in T0 (Additional file  1 : Figure S11C, G, J). These alterations in molecular–bacterial correlation are driven by metabolomics changes during antiperspirant use as revealed by metabolomics shifts on the PCoA space (Additional file  1 : Figure S11), partially due to the deodorant’s chemicals (Additional file  1 : Figure S1J, K) but also to changes observed in steroid levels in the armpits (Fig.  5A, C, D , Additional file 1 : Figure S6G), suggesting metabolome-dependant changes of the skin microbiome. In agreement with previous findings that showed efficient biotransformation of steroids by Corynebacterium [ 43 , 44 ], our correlation analysis associates specific steroids that were affected by antiperspirant use in the armpits of volunteer 11 (Fig.  5 c, d, Additional file 1 : Figure S6G) with microbes that may produce or process them: 1-dehydroandrostenedione, androstenedione, and dehydrosterone with Corynebacterium ( r  = − 0.674, p  = 6e−05; r  = 0.671, p  = 7e−05; r  = 0.834, p  < 1e−05, respectively) (Additional file  1 : Figure S12A, B, C, respectively) and Enhydrobacter ( r  = 0.683, p  = 4e−05; r  = 0.581, p  = 0.00095; r  = 0.755, p  < 1e−05 respectively) (Additional file  1 : Figure S12D, E, F, respectively).

Despite the widespread use of skin care and hygiene products, their impact on the molecular and microbial composition of the skin is poorly studied. We established a workflow that examines individuals to systematically study the impact of such lifestyle characteristics on the skin by taking a broad look at temporal molecular and bacterial inventories and linking them to personal skin care product use. Our study reveals that when the hygiene routine is modified, the skin metabolome and microbiome can be altered, but that this alteration depends on product use and location on the body. We also show that like gut microbiome responses to dietary changes [ 20 , 21 ], the responses are individual-specific.

We recently reported that traces of our lifestyle molecules can be detected on the skin days and months after the original application [ 18 , 19 ]. Here, we show that many of the molecules associated with our personal skin and hygiene products had a half-life of 0.5 to 1.9 weeks even though the volunteers regularly showered, swam, or spent time in the ocean. Thus, a single application of some of these products has the potential to alter the microbiome and skin chemistry for extensive periods of time. Our data suggests that although host genetics and diet may play a role, a significant part of the resilience of the microbiome that has been reported [ 10 , 45 ] is due to the resilience of the skin chemistry associated with personal skin and hygiene routines, or perhaps even continuous re-exposure to chemicals from our personal care routines that are found on mattresses, furniture, and other personal objects [ 19 , 27 , 46 ] that are in constant contact. Consistent with this observation is that individuals in tribal regions and remote villages that are infrequently exposed to the types of products used in this study have very different skin microbial communities [ 47 , 48 ] and that the individuals in this study who rarely apply personal care products had a different starting metabolome. We observed that both the microbiome and skin chemistry of these individuals were most significantly affected by these products. This effect by the use of products at T4–T6 on the volunteers that infrequently used them lasted to the end phase of the study even though they went back to infrequent use of personal care products. What was notable and opposite to what the authors originally hypothesized is that the use of the foot powder and antiperspirant increased the diversity of microbes and that some of this diversity continued in the T7–T9 phase when people went back to their normal skin and hygiene routines. It is likely that this is due to the alteration in the nutrient availability such as fatty acids and moisture requirements, or alteration of microbes that control the colonization via secreted small molecules, including antibiotics made by microbes commonly found on the skin [ 49 , 50 ].

We detected specific molecules on the skin that originated from personal care products or from the host. One ingredient that lasts on the skin is propylene glycol, which is commonly used in deodorants and antiperspirants and added in relatively large amounts as a humectant to create a soft and sleek consistency [ 51 ]. As shown, daily use of personal care products is leading to high levels of exposure to these polymers. Such polymers cause contact dermatitis in a subset of the population [ 51 , 52 ]. Our data reveal a lasting accumulation of these compounds on the skin, suggesting that it may be possible to reduce their dose in deodorants or frequency of application and consequently decrease the degree of exposure to such compounds. Formulation design of personal care products may be influenced by performing detailed outcome studies. In addition, longer term impact studies are needed, perhaps in multiple year follow-up studies, to assess if the changes we observed are permanent or if they will recover to the original state.

Some of the host- and microbiome-modified molecules were also detected consistently, such as acylcarnitines, bile acids, and certain steroids. This means that a portion of the molecular composition of a person’s skin is not influenced by the beauty products applied to the skin, perhaps reflecting the level of exercise for acylcarnitines [ 53 , 54 ] or the liver (dominant location where they are made) or gallbladder (where they are stored) function for bile acids. The bile acid levels are not related to sex and do not change in amount during the course of this study. While bile acids are typically associated with the human gut microbiome [ 34 , 55 , 56 , 57 , 58 ], it is unclear what their role is on the skin and how they get there. One hypothesis is that they are present in the sweat that is excreted through the skin, as this is the case for several food-derived molecules such as caffeine or drugs and medications that have been previously reported on the human skin [ 19 ] or that microbes synthesize them de novo [ 55 ]. The only reports we could find on bile acids being associated with the skin describe cholestasis and pruritus diseases. Cholestasis and pruritus in hepatobiliary disease have symptoms of skin bile acid accumulation that are thought to be responsible for severe skin itching [ 59 , 60 ]. However, since bile acids were found in over 50% of the healthy volunteers, their detection on the skin is likely a common phenotype among the general population and not only reflective of disease, consistent with recent reports challenging these molecules as biomarkers of disease [ 59 ]. Other molecules that were detected consistently came from personal care products.

Aside from molecules that are person-specific and those that do not vary, there are others that can be modified via personal care routines. Most striking is how the personal care routines influenced changes in hormones and pheromones in a personalized manner. This suggests that there may be personalized recipes that make it possible to make someone more or less attractive to others via adjustments of hormonal and pheromonal levels through alterations in skin care.

Here, we describe the utilization of an approach that combines metabolomics and microbiome analysis to assess the effect of modifying personal care regime on skin chemistry and microbes. The key findings are as follows: (1) Compounds from beauty products last on the skin for weeks after their first use despite daily showering. (2) Beauty products alter molecular and bacterial diversity as well as the dynamic and structure of molecules and bacteria on the skin. (3) Molecular and bacterial temporal variability is product-, site-, and person-specific, and changes are observed starting the first week of beauty product use. This study provides a framework for future investigations to understand how lifestyle characteristics such as diet, outdoor activities, exercise, and medications shape the molecular and microbial composition of the skin. These factors have been studied far more in their impact on the gut microbiome and chemistry than in the skin. Revealing how such factors can affect skin microbes and their associated metabolites may be essential to define long-term skin health by restoring the appropriate microbes particularly in the context of skin aging [ 61 ] and skin diseases [ 49 ] as has shown to be necessary for amphibian health [ 62 , 63 ], or perhaps even create a precision skin care approach that utilizes the proper care ingredients based on the microbial and chemical signatures that could act as key players in host defense [ 49 , 64 , 65 ].

Subject recruitment and sample collection

Twelve individuals between 25 and 40 years old were recruited to participate in this study, six females and six males. Female volunteer 8 dropped out of the study as she developed a skin irritation during the T1–T3 phase. All volunteers signed a written informed consent in accordance with the sampling procedure approved by the UCSD Institutional Review Board (Approval Number 161730). Volunteers were required to follow specific instructions during 9 weeks. They were asked to bring in samples of their personal care products they used prior to T0 so they could be sampled as well. Following the initial timepoint time 0 and during the first 3 weeks (week 1–week 3), volunteers were asked not to use any beauty products (Fig.  1 b). During the next 3 weeks (week 4–week 6), four selected commercial beauty products provided to all volunteers were applied once a day at specific body part (deodorant for the armpits, soothing foot powder between the toes, sunscreen for the face, and moisturizer for front forearms) (Fig.  1 b, Additional file  3 : Table S2 Ingredient list of beauty products). During the first 6 weeks, volunteers were asked to shower with a head to toe shampoo. During the last 3 weeks (week 7–week 9), all volunteers went back to their normal routine and used the personal care products used before the beginning of the study (Fig.  1 b). Volunteers were asked not to shower the day before sampling. Samples were collected by the same three researchers to ensure consistency in sampling and the area sampled. Researchers examined every subject together and collected metabolomics and microbiome samples from each location together. Samples were collected once a week (from day 0 to day 68—10 timepoints total) for volunteers 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, and 12, and on day 0 and day 6 for volunteer 8. For individuals 4, 9, and 10, samples were collected twice a week. Samples collected for 11 volunteers during 10 timepoints: 11 volunteers × 10 timepoints × 4 samples × 4 body sites = 1760. Samples collected from 3 selected volunteers during 9 additional timepoints: 3 volunteers × 9 timepoints × 4 samples × 4 body sites = 432. All samples were collected following the same protocol described in [ 18 ]. Briefly, samples were collected over an area of 2 × 2 cm, using pre-moistened swabs in 50:50 ethanol/water solution for metabolomics analysis or in Tris-EDTA buffer for 16S rRNA sequencing. Four samples were collected from each body part right and left side. The locations sampled were the face—upper cheek bone and lower jaw, armpit—upper and lower area, arm—front of the elbow (antecubitis) and forearm (antebrachium), and feet—in between the first and second toe and third and fourth toe. Including personal care product references, a total of 2275 samples were collected over 9 weeks and were submitted to both metabolomics and microbial inventories.

Metabolite extraction and UPLC-Q-TOF mass spectrometry analysis

Skin swabs were extracted and analyzed using a previously validated workflow described in [ 18 , 19 ]. All samples were extracted in 200 μl of 50:50 ethanol/water solution for 2 h on ice then overnight at − 20 °C. Swab sample extractions were dried down in a centrifugal evaporator then resuspended by vortexing and sonication in a 100 μl 50:50 ethanol/water solution containing two internal standards (fluconazole 1 μM and amitriptyline 1 μM). The ethanol/water extracts were then analyzed using a previously validated UPLC-MS/MS method [ 18 , 19 ]. We used a ThermoScientific UltiMate 3000 UPLC system for liquid chromatography and a Maxis Q-TOF (Quadrupole-Time-of-Flight) mass spectrometer (Bruker Daltonics), controlled by the Otof Control and Hystar software packages (Bruker Daltonics) and equipped with ESI source. UPLC conditions of analysis are 1.7 μm C18 (50 × 2.1 mm) UHPLC Column (Phenomenex), column temperature 40 °C, flow rate 0.5 ml/min, mobile phase A 98% water/2% acetonitrile/0.1% formic acid ( v / v ), mobile phase B 98% acetonitrile/2% water/0.1% formic acid ( v / v ). A linear gradient was used for the chromatographic separation: 0–2 min 0–20% B, 2–8 min 20–99% B, 8–9 min 99–99% B, 9–10 min 0% B. Full-scan MS spectra ( m/z 80–2000) were acquired in a data-dependant positive ion mode. Instrument parameters were set as follows: nebulizer gas (nitrogen) pressure 2 Bar, capillary voltage 4500 V, ion source temperature 180 °C, dry gas flow 9 l/min, and spectra rate acquisition 10 spectra/s. MS/MS fragmentation of 10 most intense selected ions per spectrum was performed using ramped collision induced dissociation energy, ranged from 10 to 50 eV to get diverse fragmentation patterns. MS/MS active exclusion was set after 4 spectra and released after 30 s.

Mass spectrometry data collected from the skin of 12 individuals can be found here MSV000081582.

LC-MS data processing

LC-MS raw data files were converted to mzXML format using Compass Data analysis software (Bruker Daltonics). MS1 features were selected for all LC-MS datasets collected from the skin of 12 individuals and blank samples (total 2275) using the open-source software MZmine [ 66 ]—see Additional file  4 : Table S3 for parameters. Subsequent blank filtering, total ion current, and internal standard normalization were performed (Additional file  5 : Table S4) for representation of relative abundance of molecular features (Fig.  2 , Additional file  1 : Figure S1), principal coordinate analysis (PCoA) (Fig.  4 ). For steroid compounds in Fig.  5 a–d, bile acids (Additional file  1 : Figure S5A-D), and acylcarnitines (Additional file  1 : Figure S5E, F) compounds, crop filtering feature available in MZmine [ 66 ] was used to identify each feature separately in all LC-MS data collected from the skin of 12 individuals (see Additional file  4 : Table S3 for crop filtering parameters and feature finding in Additional file  6 : Table S5).

Heatmap in Fig.  2 was constructed from the bucket table generated from LC-MS1 features (Additional file  7 : Table S6) and associated metadata (Additional file  8 : Table S7) using the Calour command line available here: https://github.com/biocore/calour . Calour parameters were as follows: normalized read per sample 5000 and cluster feature minimum reads 50. Procrustes and Pearson correlation analyses in Additional file  1 : Figures S10 and S11 were performed using the feature table in Additional file  9 : Table S8, normalized using the probabilistic quotient normalization method [ 67 ].

16S rRNA amplicon sequencing

16S rRNA sequencing was performed following the Earth Microbiome Project protocols [ 68 , 69 ], as described before [ 18 ]. Briefly, DNA was extracted using MoBio PowerMag Soil DNA Isolation Kit and the V4 region of the 16S rRNA gene was amplified using barcoded primers [ 70 ]. PCR was performed in triplicate for each sample, and V4 paired-end sequencing [ 70 ] was performed using Illumina HiSeq (La Jolla, CA). Raw sequence reads were demultiplexed and quality controlled using the defaults, as provided by QIIME 1.9.1 [ 71 ]. The primary OTU table was generated using Qiita ( https://qiita.ucsd.edu/ ), using UCLUST ( https://academic.oup.com/bioinformatics/article/26/19/2460/230188 ) closed-reference OTU picking method against GreenGenes 13.5 database [ 72 ]. Sequences can be found in EBI under accession number EBI: ERP104625 or in Qiita ( qiita.ucsd.edu ) under Study ID 10370. Resulting OTU tables were then rarefied to 10,000 sequences/sample for downstream analyses (Additional file  10 Table S9). See Additional file  11 : Table S10 for read count per sample and Additional file  1 : Figure S13 representing the samples that fall out with rarefaction at 10,000 threshold. The dataset includes 35 blank swab controls and 699 empty controls. The blank samples can be accessed through Qiita ( qiita.ucsd.edu ) as study ID 10370 and in EBI with accession number EBI: ERP104625. Blank samples can be found under the metadata category “sample_type” with the name “empty control” and “Swabblank.” These samples fell below the rarefaction threshold at 10,000 (Additional file  11 : Table S10).

To rule out the possibility that personal care products themselves contained the microbes that induced the changes in the armpit and foot microbiomes that were observed in this study (Fig.  7 ), we subjected the common personal care products that were used in this study during T4–T6 also to 16S rRNA sequencing. The data revealed that within the limit of detectability of the current experiment, few 16S signatures were detected. One notable exception was the most dominant plant-originated bacteria chloroplast detected in the sunscreen lotion applied on the face (Additional file  1 : Figure S9D), that was also detected on the face of individuals and at a lower level on their arms, sites where stable microbial communities were observed over time (Additional file  1 : Figure S9E, F). This finding is in agreement with our previous data from the 3D cartographical skin maps that revealed the presence of co-localized chloroplast and lotion molecules [ 18 ]. Other low-abundant microbial signatures found in the sunscreen lotion include additional plant-associated bacteria: mitochondria [ 73 ], Bacillaceae [ 74 , 75 ], Planococcaceae [ 76 ], and Ruminococcaceae family [ 77 ], but all these bacteria are not responsible for microbial changes associated to beauty product use, as they were poorly detected in the armpits and feet (Fig.  7 ).

To assess the origin of Cyanobacteria detected in skin samples, each Greengenes [ 72 ] 13_8 97% OTU table (per lane; obtained from Qiita [ 78 ] study 10,370) was filtered to only features with a p__Cyanobacteria phylum. The OTU maps for these tables—which relate each raw sequence to an OTU ID—were then filtered to only those observed p__Cyanobacteria OTU IDs. The filtered OTU map was used to extract the raw sequences into a single file. Separately, the unaligned Greengenes 13_8 99% representative sequences were filtered into two sets, first the set of representatives associated with c__Chloroplast (our interest database), and second the set of sequences associated with p__Cyanobacteria without the c__Chloroplast sequences (our background database). Platypus Conquistador [ 79 ] was then used to determine what reads were observed exclusively in the interest database and not in the background database. Of the 4,926,465 raw sequences associated with a p__Cyanobacteria classification (out of 318,686,615 total sequences), at the 95% sequence identity level with 100% alignment, 4,860,258 sequences exclusively recruit to full-length chloroplast 16S by BLAST [ 80 ] with the bulk recruiting to streptophytes (with Chlorophyta and Stramenopiles to a lesser extent). These sequences do not recruit non-chloroplast Cyanobacteria full length 16S.

Half-life calculation for metabolomics data

In order to estimate the biological half-life of molecules detected in the skin, the first four timepoints of the study (T0, T1, T2, T3) were considered for the calculation to allow the monitoring of personal beauty products used at T0. The IUPAC’s definition of biological half-life as the time required to a substance in a biological system to be reduced to half of its value, assuming an approximately exponential removal [ 81 ] was used. The exponential removal can be described as C ( t )  =  C 0 e − tλ where t represents the time in weeks, C 0 represents the initial concentration of the molecule, C ( t ) represents the concentration of the molecule at time t , and λ is the rate of removal [ http://onlinelibrary.wiley.com/doi/10.1002/9780470140451.ch2/summary ]. The parameter λ was estimated by a mixed linear effects model in order to account for the paired sample structure. The regression model tests the null hypothesis that λ is equal to zero and only the significant ( p value < 0.05) parameters were considered.

Principal coordinate analysis

We performed principal coordinate analysis (PCoA) on both metabolomics and microbiome data. For metabolomics, we used MS1 features (Additional file  5 : Table S4) and calculated Bray–Curtis dissimilarity metric using ClusterApp ( https://github.com/mwang87/q2_metabolomics ).

For microbiome data, we used rarefied OTU table (Additional file 10 : Table S9) and used unweighted UniFrac metric [ 36 ] to calculate beta diversity distance matrix using QIIME2 (https://qiime2.org). Results from both data sources were visualized using Emperor ( https://biocore.github.io/emperor/ ) [ 28 ].

Molecular networking

Molecular networking was generated from LC-MS/MS data collected from skin samples of 11 individuals MSV000081582, using the Global Natural Products Social Molecular Networking platform (GNPS) [ 29 ]. Molecular network parameters for MS/MS data collected from all body parts of 11 individuals during T0–T9 MSV000081582 are accessible here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=284fc383e4c44c4db48912f01905f9c5 . Molecular network parameters for MS/MS data collected from armpits T0–T3 MSV000081582 and deodorant used by individual 1 and 3 MSV000081580 can be found here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=f5325c3b278a46b29e8860ec57915ad and here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=aaa1af68099d4c1a87e9a09f398fe253 , respectively. Molecular networks were exported and visualized in Cytoscape 3.4.0. [ 82 ]. Molecular networking parameters were set as follows: parent mass tolerance 1 Da, MS/MS fragment ion tolerance 0.5 Da, and cosine threshold 0.65 or greater, and only MS/MS spectral pairs with at least 4 matched fragment ions were included. Each MS/MS spectrum was only allowed to connect to its top 10 scoring matches, resulting in a maximum of 10 connections per node. The maximum size of connected components allowed in the network was 600, and the minimum number of spectra required in a cluster was 3. Venn diagrams were generated from Cytoscape data http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=284fc383e4c44c4db48912f01905f9c5 using Cytoscape [ 82 ] Venn diagram app available here http://apps.cytoscape.org/apps/all .

Shannon molecular and bacterial diversity

The diversity analysis was performed separately for 16S rRNA data and LC-MS data. For each sample in each feature table (LC-MS data and microbiome data), we calculated the value of the Shannon diversity index. For LC-MS data, we used the full MZmine feature table (Additional file  5 : Table S4). For microbiome data, we used the closed-reference BIOM table rarefied to 10,000 sequences/sample. For diversity changes between timepoints, we aggregated Shannon diversity values across groups of individuals (all, females, males) and calculated mean values and standard errors. All successfully processed samples (detected features in LC-MS or successful sequencing with 10,000 or more sequences/sample) were considered.

Beauty products and chemical standards

Samples (10 mg) from personal care products used during T0 and T7–T9 MSV000081580 (Additional file  2 : Table S1) and common beauty products used during T4–T6 MSV000081581 (Additional file  3 : Table S2) were extracted in 1 ml 50:50 ethanol/water. Sample extractions were subjected to the same UPLC-Q-TOF MS method used to analyze skin samples and described above in the section “ Metabolite extraction and UPLC-Q-TOF mass spectrometry analysis .” Authentic chemical standards MSV000081583 including 1-dehydroandrostenedion (5 μM), chenodeoxyglycocholic acid (5 μM), dehydroisoandrosterone sulfate (100 μM), glycocholic acid (5 μM), and taurocholic acid (5 μM) were analyzed using the same mass spectrometry workflow used to run skin and beauty product samples.

Monitoring beauty product ingredients in skin samples

In order to monitor beauty product ingredients used during T4–T6, we selected only molecular features present in each beauty product sample (antiperspirant, facial lotion, body moisturizer, soothing powder) and then filtered the aligned MZmine feature table (Additional file  5 : Table S4) for the specific feature in specific body part samples. After feature filtering, we selected all features that had a higher average intensity on beauty product phase (T4–T6) compared to non-beauty product phase (T1–T3). The selected features were annotated using GNPS dereplication output http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=69319caf219642a5a6748a3aba8914df , plotted using R package ggplot2 ( https://cran.r-project.org/web/packages/ggplot2/index.html ) and visually inspected for meaningful patterns.

Random forest analysis

Random forest analysis was performed in MetaboAnalyst 3.0 online platform http://www.metaboanalyst.ca/faces/home.xhtml . Using LC-MS1 features found in armpit samples collected on T3 and T6. Random forest parameters were set as follows: top 1000 most abundant features, number of predictors to try for each node 7, estimate of error rate (0.0%).

BugBase analysis

To determine the functional potential of microbial communities within our samples, we used BugBase [ 83 ]. Because we do not have direct access to all of the gene information due to the use of 16S rRNA marker gene sequencing, we can only rely on phylogenetic information inferred from OTUs. BugBase takes advantage of this information to predict microbial phenotypes by associating OTUs with gene content using PICRUSt [ 84 ]. Thus, using BugBase, we can predict such phenotypes as Gram staining, or oxidative stress tolerance at each timepoint or each phase. All statistical analyses in BugBase are performed using non-parametric differentiation tests (Mann–Whitney U ).

Taxonomic plots

Rarefied OTU counts were collapsed according to the OTU’s assigned family and genus name per sample, with a single exception for the class of chloroplasts. Relative abundances of each family-genus group are obtained by dividing by overall reads per sample, i.e., 10,000. Samples are grouped by volunteer, body site, and time/phase. Abundances are aggregated by taking the mean overall samples, and resulting abundances are again normalized to add up to 1. Low-abundant taxa are not listed in the legend and plotted in grayscale. Open-source code is available at https://github.com/sjanssen2/ggmap/blob/master/ggmap/snippets.py

Dissimilarity-based analysis

Pairwise dissimilarity matrices were generated for metabolomics and 16S metagenomics quantification tables, described above, using Bray–Curtis dissimilarity through QIIME 1.9.1 [ 71 ]. Those distance matrices were used to perform Procrustes analysis (QIIME 1.9.1), and Mantel test (scikit-bio version 0.5.1) to measure the correlation between the metabolome and microbiome over time. The metabolomics dissimilarities were used to perform the PERMANOVA test to assess the significance of body part grouping. The PCoA and Procrustes plots were visualized in EMPeror. The dissimilarity matrices were also used to perform distance tests, comparing the distances within and between individuals and distances from time 0 to times 1, 2, and 3 using Wilcoxon rank-sum tests (SciPy version 0.19.1) [ 19 ].

Statistical analysis for molecular and microbial data

Statistical analyses were performed in R and Python (R Core Team 2018). Monotonic relationships between two variables were tested using non-parametric Spearman correlation tests. The p values for correlation significance were subsequently corrected using Benjamini and Hochberg false discovery rate control method. The relationship between two groups was tested using non-parametric Wilcoxon rank-sum tests. The relationship between multiple groups was tested using non-parametric Kruskal–Wallis test. The significance level was set to 5%, unless otherwise mentioned, and all tests were performed as two-sided tests.

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Acknowledgements

We thank all volunteers who were recruited in this study for their participation and Carla Porto for discussions regarding beauty products selected in this study. We further acknowledge Bruker for the support of the shared instrumentation infrastructure that enabled this work.

This work was partially supported by US National Institutes of Health (NIH) Grant. P.C.D. acknowledges funding from the European Union’s Horizon 2020 Programme (Grant 634402). A.B was supported by the National Institute of Justice Award 2015-DN-BX-K047. C.C. was supported by a fellowship of the Belgian American Educational Foundation and the Research Foundation Flanders. L.Z., J.K, and K.Z. acknowledge funding from the US National Institutes of Health under Grant No. AR071731. TLK was supported by Vaadia-BARD Postdoctoral Fellowship Award No. FI-494-13.

Availability of data and materials

The mass spectrometry data have been deposited in the MassIVE database (MSV000081582, MSV000081580 and MSV000081581). Molecular network parameters for MS/MS data collected from all body parts of 11 individuals during T0-T9 MSV000081582 are accessible here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=284fc383e4c44c4db48912f01905f9c5 . Molecular network parameters for MS/MS data collected from armpits T0–T3 MSV000081582 and deodorant used by individual 1 and 3 MSV000081580 can be found here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=f5325c3b278a46b29e8860ec5791d5ad and here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=aaa1af68099d4c1a87e9a09f398fe253 , respectively. OTU tables can be found in Qiita ( qiita.ucsd.edu ) as study ID 10370, and sequences can be found in EBI under accession number EBI: ERP104625.

Author information

Amina Bouslimani and Ricardo da Silva contributed equally to this work.

Authors and Affiliations

Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, San Diego, USA

Amina Bouslimani, Ricardo da Silva, Kathleen Dorrestein, Alexey V. Melnik, Tal Luzzatto-Knaan & Pieter C. Dorrestein

Department of Pediatrics, University of California, San Diego, La Jolla, CA, 92037, USA

Tomasz Kosciolek, Stefan Janssen, Chris Callewaert, Amnon Amir, Livia S. Zaramela, Ji-Nu Kim, Gregory Humphrey, Tara Schwartz, Karenina Sanders, Caitriona Brennan, Gail Ackermann, Daniel McDonald, Karsten Zengler, Rob Knight & Pieter C. Dorrestein

Department for Pediatric Oncology, Hematology and Clinical Immunology, University Children’s Hospital, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany

Stefan Janssen

Center for Microbial Ecology and Technology, Ghent University, 9000, Ghent, Belgium

Chris Callewaert

Center for Microbiome Innovation, University of California, San Diego, La Jolla, CA, 92307, USA

Karsten Zengler, Rob Knight & Pieter C. Dorrestein

Department of Bioengineering, University of California, San Diego, La Jolla, CA, 92093, USA

Karsten Zengler & Rob Knight

Department of Computer Science and Engineering, University of California, San Diego, La Jolla, CA, 92093, USA

Department of Pharmacology, University of California, San Diego, La Jolla, CA, 92037, USA

Pieter C. Dorrestein

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Contributions

AB and PCD contributed to the study and experimental design. AB, KD, and TLK contributed to the metabolite and microbial sample collection. AB contributed to the mass spectrometry data collection. AB, RS, and AVM contributed to the mass spectrometry data analysis. RS contributed to the metabolomics statistical analysis and microbial–molecular correlations. GH, TS, KS, and CB contributed to the 16S rRNA sequencing. AB and GA contributed to the metadata organization. TK, SJ, CC, AA, and DMD contributed to the microbial data analysis and statistics. LZ, JK, and KZ contributed to the additional data analysis. AB, PCD, and RK wrote the manuscript. All authors read and approved the final manuscript.

Corresponding authors

Correspondence to Rob Knight or Pieter C. Dorrestein .

Ethics declarations

Ethics approval and consent to participate.

All participants signed a written informed consent in accordance with the sampling procedure approved by the UCSD Institutional Review Board (Approval Number 161730).

Competing interests

Dorrestein is on the advisory board for SIRENAS, a company that aims to find therapeutics from ocean environments. There is no overlap between this research and the company. The other authors declare that they have no competing interests.

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Additional files

Additional file 1:.

Figure S1. Beauty products ingredients persist on skin of participants. Figure S2. Beauty product application impacts the molecular and bacterial diversity on skin of 11 individuals while the chemical diversity from personal beauty products used by males and females on T0 is similar. Figure S3. Longitudinal impact of ceasing and resuming the use of beauty products on the molecular composition of the skin over time. Figure S4. Molecular networking to highlight MS/MS spectra found in each body part. Figure S5. Longitudinal abundance of bile acids and acylcarnitines in skin samples. Figure S6. Characterization of steroids in armpits samples. Figure S7. Characterization of bile acids in armpit samples. Figure S8. Characterization of Acylcarnitine family members in skin samples. Figure S9. Beauty products applied at one body part might affect other areas of the body, while specific products determine stability versus variability of microflora at each body site. Figure S10. Representation of Gram-positive bacteria over time and the molecular features from the shampoo detected on feet. Figure S11. Procrustes analysis to correlate the skin microbiome and metabolome over time. Figure S12. Correlation between specific molecules and bacteria that change over time in armpits of individual 11. Figure S13. Representation of the number of samples that were removed (gray) and those retained (blue) after rarefaction at 10,000 threshold. (DOCX 1140 kb)

Additional file 2:

Table S1. List of personal (T0 and T7–9) beauty products and their frequency of use. (XLSX 30 kb)

Additional file 3:

Table S2. List of ingredients of common beauty products used during T4–T6. (PDF 207 kb)

Additional file 4:

Table S3. Mzmine feature finding and crop filtering parameters. (XLSX 4 kb)

Additional file 5:

Table S4. Feature table for statistical analysis with blank filtering and total ion current normalization. (CSV 150242 kb)

Additional file 6:

Table S5. Feature table for individual feature abundance in armpits. (XLSX 379 kb)

Additional file 7:

Table S6. Feature table for Calour analysis. (CSV 91651 kb)

Additional file 8:

Table S7. Metadata for Calour analysis. (TXT 129 kb)

Additional file 9:

Table S8. feature table with Probabilistic quotient normalization for molecular–microbial analysis. (ZIP 29557 kb)

Additional file 10:

Table S9. OTU table rarefied to 10,000 sequences per sample. (BIOM 9493 kb)

Additional file 11:

Table S10. 16S rRNA sequencing read counts per sample. (TSV 2949 kb)

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Bouslimani, A., da Silva, R., Kosciolek, T. et al. The impact of skin care products on skin chemistry and microbiome dynamics. BMC Biol 17 , 47 (2019). https://doi.org/10.1186/s12915-019-0660-6

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10 Thesis Topics in Dermatology: How to Choose, How and Where to Research

Dermatology is a field of science that deals with the study of skin, nails, hair and its treatment in case of various complications. Selecting thesis topics in dermatology should be based on the sphere of interest and acquired knowledge obtained during the course. While choosing a particular topic, the researcher should pay attention to the innovative technological therapies that are elaborated to struggle with skin conditions. Thesis topics in dermatology should focus on the analysis of various surgeries, influence of a person’s lifestyle on the skin, and the relation of the skin condition to other diseases.

In this article, you are offered the list of 10 topics acceptable for dermatology theses – one of the research questions is answered for visual reference. Be sure that these dermatology topics are chosen according to the proper procedure that is also explained in this article. Besides, you’ll find 5 simple and effective ways to do research on dermatology topics. So read it attentively paying attention to all the details.

Table of Contents

10 Dermatology Topics: Be Open to New Thesis Ideas to Research

Don’t know what to research in Dermatology? Indeed, there are many possible dermatological issues that require a lot of attention on the part of researchers. But it is true that there may be difficulties in choosing a good dermatology topic, especially if you need to write a thesis that amounts to 50% of the overall grade. Among the key problems most students face while selecting a research topic, it is possible to highlight the following ones:

• There is no relevant information because the research topic has been only under close investigation;
• There is too much information because the topic is debatable and every researcher has his/her own point of view.

These 2 issues are taken into consideration while compiling the following list of 10 dermatology topics. It means that enough information is available to you to write a well-researched thesis on Dermatology. Below you’ll find the reliable sources of information.

• The Epidemiological Investigation of Uncommon Skin Disorders:
• Top 5 Risk Factors of Melanoma and Nonmelanoma Skin Cancers;
• The Genetic Test for Uncommon Skin Conditions;
• The Interaction Between Genetic and Environmental Factors for Skin Disorders;
• Genetic Changes within the FLG Gene and Negative Environmental Challenges for a Proper Skin Barrier;
• The Neonatal Skin Care Preventing the Development of AD;
• The Identification of Potentially Novel Skin Disorders within Technological Environment;
• The Interaction of Pharmaceutical and Cosmetic Agents for the Improvement of the Skin Barrier;
• Skin Manifestations of Autoimmune Disorders or Side Effects of Medication;
• The Effectiveness of Cosmetic Products in Treating Atopic Dermatitis.

10 Information Sources to Research a Dermatology Thesis Topic

It is vital to have reliable sources of information at hand before you start writing a thesis. Don’t skip this stage and start examining the following sources to write your own thesis:

• American Journal of Clinical Dermatology is a journal presenting the evidence-based articles and clinically focussed studies covering all aspects of dermatology.
• Annals of Dermatology is an official peer-reviewed publication of the latest research outcomes and recent trends in dermatology.
• Dermatology Case Reports Journal is a peer-reviewed journal that includes a wide range of topics in this field including Cosmetic Dermatology, Dermatology, Cosmetic Surgery, skin disorders, Dermatological Oncology, Dermatopathology, cutaneous lymphoma.
• Clinical, Cosmetic and Investigational Dermatology is a peer-reviewed journal covering the latest clinical and experimental research in all aspects of skin disease and its cosmetic interventions.
• Clinical Dermatology and Dermatitis is a peer-reviewed medical journal sharing the useful knowledge of clinicians, medical practitioners.
• Journal of the American Academy of Dermatology is a peer-reviewed journal containing official and scientific publications and aiming to satisfy the educational needs of the dermatology community.
• Journal of Investigative Dermatology is a peer-reviewed journal that is related to all aspects of cutaneous biology and skin diseases.
• JAMA Dermatology is is a monthly peer-reviewed journal by the American Medical Association that covers the diagnosis and treatment of all possible dermatological issues.
• The Skin Cancer Foundation is an international organization providing the public and the medical community with information about skin cancer. For example, you can examine some skin cancer facts and statistics to support your own research or essay.
• The Society for Melanoma Research is an organization formed by scientific and medical investigators to alleviate the suffering of people with melanoma.

3 Points to Choose the ‘Best’ Topic for a Thesis

Good research depends on many factors, and a well-chosen topic is that you should start with. You can know how to write and edit a thesis properly, but the final quality of the research process will depend on what topic is chosen. Make sure that the following points are applied to your thesis topic:

• Originality. A degree of originality is a key requirement for academic writing. Everyone hears about plagiarism issues at colleges or universities. In the case when you take into consideration the same topic that has been already explored, nobody will punish for that. However, you should keep in mind that it won’t be highly appreciated as well. Try to shed light on the issue from another perspective if you’ve already chosen an investigated matter. Otherwise, you risk not standing out in the academic field. Hopefully, you won’t pursue this path.
• Research interests. Always when you are short of ideas to cover, rely on the research interests – think of what could be interesting for people both in and outside the field of study, and get them excited about your research. In other words, your thesis should lead to answers for big important questions that are in mind of people.
• Manageability. Remember that developing any research idea means investing enough time and energy. However, there are some topics that are easy to consider, but much harder to write on. Think of the simplest way you will do your research, and how you would go about it. As a result, you should press ahead with the simple action plan first. Only then, you can make a final choice.

Although all these points play a great role in choosing a well-run topic for a thesis, you should stay within the proper context of the field of study to answer a research question to the fullest extent – an average idea that is well-executed is much better than a brilliant idea that is executed badly. Remember it and look at the example of writing on one of the dermatology topics.

The Impact of Hormones on the Skin

First and foremost, disbalance of hormones affects human skin that is caused by the number of problems such as consumption of non-organic food, inappropriate diet, and sugar balance, lack of sleep and exercise, and stress. Hormones are deeply integrated into chemical signals created in organs including adrenal glands, ovaries, and thyroid glands that influence other tissues. Estrogen, testosterone, and thyroid are the most important hormones that need to be regulated to have healthy skin and keep the body organism in balance.

Estrogen is primarily considered to be the female hormone that controls the reproductive system and fertility/libido levels. The decline of estrogens leads to the dehydration and poor skin as well as a small amount of blood flow to the skin. The skin becomes thin and sallow losing the accurate lines and healthy look. As a result, the wrinkles appear; the skin around the lips and eyes sags and loses its vibrancy.

To keep estrogens in balance, the person should consume natural foods adding flax seeds and soy to the diet that fasten estrogen metabolism. It helps to prevent the excess level of the hormone and protect the organism from such dangerous disease as breast cancer. Furthermore, herbs involving hops, maca, and black cohosh can also be used to increase estrogen levels in women. Bio-identical hormone therapy under the control of the well-trained professional can also be beneficial to regulate estrogen level.

Testosterone is a principally male hormone that is responsible for muscle and fat gain as well as stimulation of libido. This hormone helps to produce the sebum that is essential to keep the skin moist and nurturing. During the period of puberty and menopause, the levels of testosterone are on the rise that makes the skin too oily. That is why, in the teenage, individuals suffer from acne that may continue in the adult age if it is not treated. To manage hormone, people are recommended to avoid consuming dairy products and eat foods rich in zinc and omega.

The thyroid is another hormone which imbalance can cause dry skin or its thickening with reduction of sweat. On the contrary, the abundance of thyroid results in the smooth, flushed, and sweaty skin. The thyroid imbalance is exacerbated when the patient also faces difficulties with digestion and proper metabolism as well as fatigue. To improve the condition of the skin, one needs to consume fatty acids involving omega-3 that are present in walnuts, salmon, algae, and eggs. The poor diet lacking these fats leads to acne and makes the skin dry.

Now, we are sure our extensive experience and research enable us to reliably offer you the best, and the most current, options available – writing on any topic you wish.

Hopefully, we are useful for you so that you can say, “I manage to do my thesis as expected from me”.

Too busy to write your paper by yourself?

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Dermatology Thesis Topics for MD/DNB

Remember Subscribing to the premium thesis topics not only will enable you to browse through premium thesis topics but also you will get access to online guidance about synopsis writing, sample size calculation, inclusion and exclusion criteria and guidance throughout thesis writing. In case you dont subscribe still do not hesitate to contact me for guidance.

Below is the list of 100 free thesis topics for MD/DNB Dermatology. You can select any good Dermatology thesis topics for MD/DNB from here. For more thesis topics you can avail the service of premium thesis topics. The premium thesis topics include list of 2000+ Dermatology thesis topics as well as recent topics which has been published in various national and international Dermatology journals. 

• Autologous serum skin test and autologous serum therapy in chronic idiopathic urticaria.
• A randomised controlled trial to compare effectiveness of skin microneedling and platelet rich plasma combination versus skin microneedling alone in the management of acne scars.
• To study efficacy of short contact therapy with topical tretinoin in acne vulgaris. A clinico – epidemiological study and therapeutic efficacy of chemical peels in management of melasma : A pilot study.
• A case control study of metabolic syndrome in psoriasis vulgaris patients at tertiary care institute. Clinical profile and patch test results among hand eczema patients at a tertiary care institute.
• Clinicopathological study of cutaneous tumours.
• Comparison of monotherapy with topical 5% minoxidil and combination therapy of topical 5% minoxidil with intradermal platelet-rich plasma via mesotherapy in androgenetic alopecia in males.
• Clinico-epidemiological profile of deformities among leprosy patients in a rural tertiary care Hospital in central india.
• To study the safety and efficacy of fractional CO2 laser with surface ablation followed by fibroblast growth factor therapy (melgain) in the treatment of idiopathic guttate hypomelanosis.
• Clinical profile of patients with acne with polycystic ovarian syndrome.
• Study of safety and efficacy of intralesional immunotherapy using tubrculin PPD in treatment of viral warts.
• To study the prevalence of oral lesions in patients attending dermatology department.
• An observational study on cutaneous adverse effects of chemotherapeutic agents.
• Clinical status and histopatology of new hansen’s cases.
• To study the cutaneous manifestations in patients of diabetes mellitus.
• A comparative study of imiquimod 5% cream versus 10% potassium hydroxide solution versus tretinoin 0.05% cream for molluscum contagiosum in children.
• A split face comparative study to evaluate efficacy of combined subcision & autologous platelet rich plasma and subcision alone for treatment of post-acne scars.
• Study of various investigative modalities in establishing the cause of chronic urticaria.
• ABO blood groups and its correlation with inherited thrombophilia in patients with venous thromboembolism.
• Evaluation of a new fourth generation rapid immuno-chromatographic screening test for detection of HIV P24 antigen and andibodies to HIV1 and 2 during screening of voluntary blood
• Study of role of skin surface biopsy in superficial cutaneous fungal infections.
• To study the efficacy of narrow band ultraviolet B therapy in different dermatological conditions.
• Clinical spectrum of dermatophytosis.
• To study demographic and phenomenal characteristics of patients of acne vulgaris and.
• To study hair cycle dynamics in men with androgenetic alopecia.
• Correlation of dermoscopic features with clinical and histopathological diagnosis of hypopigmented skin lesions.
• A clinical study of acne scars and the efficacy and safety of 100% Trichloroacetic acid (TCA) chemical reconstriuction of skin scars (cross) in ice-pick scars.
• A clinico-epidemiological and investigative study of premature greying of hair.
• Clinico-histopathological correlation of various photodermatoses
• Role of skin prick test for food allergies in urticaria
• To study the effect of chemical peeling in various dermatological conditions
• Clinico-histopathological study of Lichen planus
• Clinicomycological correlation of dermatophytosis
• Skin changes and disorders asso. with pregnancy
• Clinical study of geriatric dermatoses
• Pattern of facial dermatoses through the ages
• Cutaneous manifestations in patients of CRF on hemodialysis
• Skin changes in endocrinological disorders other than diabetes mellitus
• Clinico-histopathological correlation of papulosquamous disorders
• Dermatoses in pediatric population in a semi- urban area
• Mucocutaneous manifestations of HIV and its correlation with CD4 count Oral lesions
• Clinocopathological differentiation between hand eczemas and hand psoriasis
• Clinicohistopathological correlation of pemphigus
• Cutaneous manifestations in diabetes mellitus
• Clinicaohistopathological study of pityriasis rosea
• Skin changes in neonates
• Clinico-etiological correlation in patients with hand eczema
• Clinico-histopath and IF correlation of vesiculobullous disorders
• Clinico-histopath study on verruca vulgaris
• Clinico-epidemiological study on pityriasis versicolor
• Quality of life in acne vulgaris and its relationship to clinical severity
• Evaluation of skin disorders in teenagers
• Clinical and histopath study of photosensitive disorders
• Clinical and histopath correlation of skin lesions in leprosy
• Clinico aetiological study of folliculits
• Clinical and histopathological study of psoriasis
• Clinical and Bacteriological study of Impetigo
• Clinical and mycological study of onychomycosis
• Clinicoepidemiological study of nail disorders.
• Clinical and epidemiological study of foot eczema
• Association of metabolic syndrome with psoriasis and its relationship to clinical severity
• Dermatoses in obesity
• Clinicoepidemiological study of alopecia in females
• Study of dermatoses in psychiatric patients
• Whole body genome exome sequencing of blood and skin derived DNA to understand germline and somatic variation in genome in vitiligo subjects
• Quality of life in melasma and its relationship to clinical severity.
• Association of metabolic syndrome with vitiligo and its relationship to clinical severity
• Comparative study of PUVA vs NBUVB vs P-NBUVB for treatment in patients with non-segmental vitiligo
• Clinico-histopathological study of Lichen Planus
• Dermoscopic study of papulosquamous skin diseases
• Investigation of predisposing factors in familial cases of vitiligo
• Quality of life in males with androgenetic alopecia.
• Quality of life in lichen planus.
• Study of the effects of chemical peeling in various dermatological condition.
• Dermoscopic study of scalp dermatoses.
• Comparative study of intralesional platelet rich plasma vs intralesional triamcinolone acetonide in the treatment of alopecia areata.
• Clinico-epidemiological study of genodermatoses.
• Comparative analysis of quality of life in patients having hand eczema via-a-vis foot eczema.
• Comparative Study Of Topical Minoxidil (5%) And Intralesional Triamcinolone Acetonide (5mg/Ml) In Treatment Of Alopecia Areata In Treatment Of Alopecia Areata Of Scalp
• Clinico-Mycological Profile Of Dermatophytosis
• A Clinico–Epidemiological Study Of Skin Conditions In Postmenopausal Women <65 Years Of Age Hailing From Pimpri Chinchwad Area Of Pune District Of Maharashtra
• Clinico–Epidemiological Study Of Facial Hyperpigmentation And Quality Of Life In These Patients
• Comparative Study Of Clinical Efficacy And Side Effects Of Oral Isotrenoin As Daily, Alternate, Pulse And Low Does Therapy In Moderate To Severe Acne
• Quality Of Life In Chronic Urticaria And Its Relationship To Clinical Severity
• Clinico–Epidemiological Study Of Topical Corticosteroids Abuse On Skin And Its Effects
• A clinico-histopathological study of nevi
• Quality of life in keloid and hypertrothic scars and its relationship to clinical severity
• Quality of life in patient with alopecia areata
• Quality of life in patients with premature canities
• Role of contact allergens in discoid eczema
• Cross sectional study of serum vitamin D levels in patients of psoriasis
• Cutaneous manifestations in patients with chronic kidney disease on hemodialysis
• Clinico-Epidemiological Study Of Phakomatoses
• Study Of Patterns Of Dermatoses In Paediatric Attendees Of A Tertiary Care Hospital At Pune
• A Study On Dermatological Manifestations Of Chronic Venous Insufficiency
• Quality Of Life In Patients With Dermatophytosis
• Clinico-Epidemiological Study Of Pmle& Biochemical Correlation Of Thyroid Dysfunction
• Assessment Of Subclinical Atherosclerosis In Patients Of Psoriasis With And Without Metabolic Syndrome
• Identification Of Isolates By Mycological Culture And Minimum Inhibitory Concentration Of Terbinafine And Itraconazole In Recalcitrantt Dermatophyte Infections
• Dermoscopic Study Of Nail Lesions In Various Dermatoses
• Evaluation Of Skin Prick Test In Urticaria
• Clinicodermoscopic Study Of Non Scarring Hair Loss In Females.

Disclaimer!

There are many methods of sample size determination. It is one of the first hurdle when someone starts writing a thesis. I have tried to give simplest way of determination of sample size. You need to show the method to your PG teacher before you include this method in your thesis. First confirm from your PG teacher and then only proceed.

Recent and Current Projects

With the exciting advances that are continuously being made in dermatology, there is increasing need to understand the multiple components of dermatologic disease to maximize benefit to patients.  The Vashi Lab’s continued mission is to apply the highest standards of care and rigorous evaluation to questions in dermatology.  We combine clinical expertise with analytical approaches to understand the skin and dermatologic disease in order to improve patient outcomes while advancing healthcare delivery.

Dr. Vashi’s research interests include a wide variety of topics related to both medical and cosmetic dermatology.  A few of her recent projects are described below.

Societal obsession with beauty is deeply engrained in our past, with the appreciation of human aesthetics dating back to early Greek civilization.  Both personal preferences and cultural standards influence our ideas on beauty, and there is substantial agreement as to what constitutes human beauty within a society at any given point in time. In the study below, Dr. Vashi examined how our societal perceptions of beauty have changed over the past 27 years using People Magazine’s World’s Most Beautiful lists from 1990 and 2017.

Maymone MBC, Neamah HH, Secemsky EA, Kundu RV, Saade D, Vashi NA. The Most Beautiful People: Evolving Standards of Beauty. JAMA Dermatol. Published online October 11, 2017. doi:10.1001/jamadermatol.2017.3693

Dr. Vashi had over 100 media exposures including but not limited to NBC News, NewsWeek, MSN News, USNews, Yahoo News, GoodHousekeeping, ABC News, Bazaar, Cosmopolitan, and Chicago Tribune in reference to this study.  With an international presence, it had translation and media exposures in over 20 different countries and languages.  In addition, it was rated the #2 “Most Talked About Article of 2017” by JAMA Dermatology .

See  NBC News’ discussion of the findings of Dr. Vashi’s study in the article “ What Makes Someone ‘Most Beautiful’ Is Changing, Study Says .”

Sun Protection

Hyperpigmentation, a common issue seen by dermatologists, can worsen when exposed to the sun. The study below explores the different ways that patients with hyperpigmentation protect themselves from the sun’s harmful UV rays.

Maymone M, Neamah HH, Wirya SA, Patzelt NM, Zancanaro PQ, Vashi NA. Sun protective behaviors in patients with cutaneous hyperpigmentation: A cross-sectional study. J Am Acad Dermatol. 2017;76(5):841–846.e2.

In April 2017, Yahoo! News published the article “ How Hyperpigmentation Patients Shield Themselves from the Sun ” describing Dr. Neelam Vashi’s findings.

Melasma is a common disorder of hyperpigmentation that can worsen when exposed to the sun and is often difficult to treat. Thus, it is important to know the extent of disease to provide proper patient counseling and treatment guidance. Dr. Neelam Vashi researched different techniques as aids for diagnosing disease extent.

Wirya SA, Maymone MBC, Widjajahakim R, Vashi NA. Subclinical melasma: Determining disease extent. J Am Acad Dermatol. 2017;77(2):e41-e42.

Dr. Neelam Vashi was interviewed on this subject by WCVB-TV, Channel 5.

Aging of the skin is clinically described by wrinkles, sunspots, uneven skin color, and sagging skin; however, these signs vary across ethnicity. This article looks at how variations in cutaneous aging are related to differences in skin structure and function.

Vashi NA, Maymone M, Kundu RV. Aging differences in ethnic skin. J Clin Aesthet Dermatol. 2016;9(1):31-38.

Dr. Neelam Vashi appeared in the article “ Outsmart Aging. Your ethnicity plays a major role in how your skin matures. Face down our challenge with a personalized plan. ” featured in Dr. Oz’s The Good Life magazine.

120 Cosmetics Essay Topic Ideas & Examples

🏆 best cosmetics topic ideas & essay examples, ✍️ cosmetics essay topics for college, 👍 simple & easy cosmetics essay titles, 🥇 good research topics about cosmetics, ❓ research questions about makeup.

• Cosmetic Testing on Animals The surface of the skin or near the eyes of such animals is meant to simulate that of the average human and, as such, is one of easiest methods of determining whether are particular type […]
• Mac Cosmetics Company’s Social Media Use for Customer Engagement The aim of this research is to determine the role of the social media in creating customer engagement to MAC Cosmetics, focusing on the United Arab Emirates’ population.
• Foundation Makeup in the Fashion When choosing a foundation for your skin, look at the bottle, and check if the skin type is listed because it will give you information about the ingredients that will match your oily skin.
• Makeup Techniques: “The Wizard of Oz” by Victor Fleming Also, the color of his face is ochre, which reminds of sacking. In general, Lion is a rather impressive character because of the makeup he has.
• Luxury Cosmetics Branding and Pricing It is considered that “beauty products appeal to the emotions and customers tend to choose based on the product image,” yet luxury brands, such as Chanel, usually emphasize the quality of cosmetics and the technology […]
• Lush Fresh Handmade Cosmetics: Brand Image Thesis: Lush Fresh Handmade Cosmetics maintains the consistency of their brand image of a sustainable, natural, and eco-friendly beauty product by encouraging recycling, using package-less practices, choosing natural and vegan materials to produce their cosmetics, […]
• Testing Makeup Products on Rabbits The use of rabbits to test the effects of body makeup harm the mental health of scientists. Despite these harmful effects of using rabbits as test animals in the screening of beauty products, experimenting chemicals […]
• Organic and Non-Organic Makeup These groups are organic and non-organic. One of the benefits of organic makeup is its apparent safety.
• How Does the Makeup Help to Define the Character For example, a well-known movie “Dorian Gray” tells to the audience the story of the lovely young man Dorian Gray who comes to London, as now he is rich; he has got a huge inheritance […]
• Analysis of Cosmetics as a Consumer Product Improvement of communication and information technology has contributed to advanced forms of advertisement that promote the consumption and exploitation of markets down to the most localized places within the global village.
• Gender and Sexuality in Cosmetic Advertising It also assesses the correctness of truths conveyed to and the effect of these advertising images to the audience. The woman’s position to the back could be interpreted as a sign of feminine subordination.
• Competition in the U.S. Cosmetics Industry At the moment, the cosmetics market in the U. The high level of rivalry peculiar to the beauty and personal care market demands an improved understanding of the competitive landscape.
• Natural Cosmetic Skincare Products Market The trends in the UK market are quite similar to the trends in the European market. There is fierce competition for the market share of natural skincare products.
• Makeup for African American Women and Its Cultural Perspective In assuring innovation in the makeup of African American women, designers must aim to comprehend the significance and comprehension of the African art culture.
• Isopropyl Alcohol in Cosmetics and Medicine Isopropyl is synthesized in two steps: through the reaction of propylene with sulfuric acid and the consequent hydrolysis. In the context of isopropyl alternatives as sanitizers, ethyl alcohol serves as a solid option.
• Racial Discrimination Through the Cosmetics Industry The variety of preconceptions such as the hypersexuality of black women and the perception of their beauty as an unideal version of whites’ one also indicates racism.
• Black Women and the Cosmetics Industry While the industry experienced a significant increase in revenue and scale, the source of this process was the racial discrimination of black women since the marketing campaign emphasized that black women are beautiful.
• Female Consumers on Luxury Brand Clothing Over Cosmetics Consumption The findings of this study suggests that the majority of the respondents preferred to spend more on clothing, although luxury brand clothing preference was notable only to a minority of the respondents.
• Knowing One’s DNA Genetic Makeup: Pros and Cons In addition, the knowledge that one might not get a job or insurance because of their genetic makeup is stressful and depressive.
• Increment of Trans Fats in Dietary Make-Up a Misguided Move Saturated fats are markedly dangerous for human health because they increase the level of the “bad” cholesterol in the body, which increases the risk of heart attacks and other heart diseases.
• AG Hair Cosmetics: Style With Substance We are a company that’s driven by the passion, and determination of our employees and artists spreading the infectious AG philosophy.
• The Chemistry Behind Mineral Make-Up According to the US Food and Drug Administration, cosmetics include all compounds or products that are applied to the body with the aim of beautifying, boosting attractiveness or improving the physical appearance without generally altering […]
• Cultural Artifact Advertisement of Makeup People have accumulated the knowledge, values, beliefs, and attitudes to the whole scope of objects they have ever known in the cultural heritage and have become inherently able to transmit it to successive generations who […]
• Advertisement Impact on Potential Buyers in the Cosmetic Industry Thus, looking at how various products are being advertised, one cannot fail to note the seriousness of the product owners in as far as convincing the consumers to fall for the given product.
• Dr. Eris Cosmetics Company From Poland Here it must be noted that I do not agree to the statement of the Polish manager who states that the small and mid-sized manufacturers have no future in the cosmetics industry.
• Cosmetics Industry and Female Identity While many are willing to pin the blame for this attitude on the women themselves, there is plenty of evidence suggesting it is a concept perpetuated and emphasized by the cosmetics industries through the medium […]
• “Clearing Up Cosmetic Confusion” and “The Great Pretenders?” The author uses a method of observations and personal experience to describe the current state of the corporate regulations within the cosmetics industry.
• Make-Up Throughout the World History In the Fiftiesweb website, the basis of any fifties make-up look is “peaches and cream complexion”. Make-up became more bold and daring in the 1960s.
• A Second Look At Yourself With the Aid of Make-Up It can be inferred now that all make-up dates back to the past and is struck by the ludicrous reasons and ways people made use of make-up.
• Cosmetics as a Decorative Technique Used by Women At the beginning of the 20th century, makeup was used to protect and project a sense of self. For me, makeup means the possibility to create and underline a unique identity and the self.
• Halal Cosmetic Products: Innovation Management Finally, the company has to transparently state its commitment to halal cosmetics in order to attract the attention of customers and enter the competition.
• Celebrity Effect & Price Advantage: Kylie Cosmetics It features a detailed analysis of the possible reasons for it and compares the history of the enterprise to the Estee Lauder Companies, a large business that was established in the middle of the 20th […]
• New Product Campaign Pitch: Women Cosmetic The target market for the marketing campaign of the new women’s cosmetics is mainly women aging from 15 to 45 in Australia.
• La Roche-Posay Cosmetics in European Market It is within this context that the essay examines the European market of LRP by analyzing the beauty market, competition, positioning strategy, identifying brand consumers, examining market trends, and the type of innovations evident in […]
• Biofilm Prevention After Cosmetic Injection The concept of biofilm remains relatively new to dermatology, with few studies available on the formation of biofilm post-cosmetic injections; however, it is needed to explore the ways of preventing biofilm formation from reducing the […]
• Business in the US Cosmetic Retailing Industry US cosmetics retailing industry tends to expand within the domestic and international markets because of the rising level of discretionary income in the developed and developing countries.
• Entrepreneurship in the Organic Cosmetics Sphere According to the article, customers want to be green, and they want to contribute to making the world better. In conclusion, it is possible to note that the article in question provides particular points in […]
• The Peculiar Features of Organic Cosmetics’ Business Gewirtz’s “Organics of Scale” and Traber’s “Experts Sound Alarm on ‘Dirty Dozen’” are the two articles that can be used by people, who want to run a company on organic cosmetics, as these sources provide […]
• Dr. Irena Eris Cosmetics Limited Case Because the Polish cosmetics industry has become saturated with the entry of more players, the firms in the market need to adjust their business strategies both internally and externally, to survive.
• Using Facebook for Multinational Cosmetics Companies In this research proposal, I will discuss the research methodology with the focus on data collection and analysis of the appropriateness of close reading and focus group methods to answer the formulated research questions in […]
• Organic Cosmetics: Shaping Consumer Behavior This will lead to an increase in the market share enjoyed by individual organic cosmetic companies and individual brand owners of organic cosmetic products.
• Ruby & Millie Make-Up Brand Public media and press played essential role in the success of Ruby & Millie brand development as advertising is an important part of products promotion.
• Factors Affecting the Consumption of Men’s Cosmetic Products The main aim of this study was to determine the factors that affect the consumption of cosmetic products in the male population.
• Characteristics of the Skin Care and Cosmetic Industry in China L’Oreal is the market leader in Chinese cosmetic and skin care industry. The success of cosmetic and skin care products companies depends on women consumers.
• Skin Care and Cosmetic Industries in China The skin care and cosmetic industries in China are divided into male and female ones and it is possible to notice the tendency of the men’s skin care industry development increase.
• The Extent of the Cosmetic Industry in Australia The use of advertising in the promotion of the marketability of this product is a strategy that Procter & Gamble has effectively developed across Australia and the rest of the international market.
• Fashion Makeup: Blumarine Fall 2010 Collection In 1980 the Blumarine brand started to become extremely successful, and the first step to popularity, traditionally to all the great brands, was made in Milan.
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• The History of Cosmetics and the Trends in the Fashion Industry
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• What Are the Tips and Tricks for Eye Makeup and Eyeshadow?
• How Has Sustainable Design Affected the Cosmetics Industry?
• Why Is the Black Market for Counterfeit Cosmetics Thriving?
• Does Wearing No Makeup Prevent Aging?
• What Are the 5 Main Categories of Cosmetic Products?
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• Is It Profitable to Use Peptides Obtained from Plants and Microalgae as Bioactive Compounds in Cosmetics?
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• How Do Cosmetics Affect Confidence, Body-Esteem, and Self-Worth?
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• What External Environmental Factors Affect the Cosmetics Industry?
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• How Do Cosmetics Contribute to the Portrayal of False Femininity in Fashion?
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• Do Makeup Courses Pave the Way to a Glamorous Career?
• What Is the Most Serious Skin Disorder Caused by Cosmetics?
• How Are the Cosmetics Industry and the Cultural Obsession with Beauty Related?
• What Are the Different Types of Skin Tones for Makeup?
• Is Going Organic the Future of Cosmetics?
• Which Cosmetics Are Absolute Must-Have for a Glamorous Look?
• Should Women Wear Makeup and Do the Hair for Themselves?
• What Are the Ingredients for Natural Cosmetics?
• Is There a Connection Between Cosmetics and Chronic Diseases?
• What Is the Ugly Truth Behind Cosmetics and Animal Testing?
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• Exploring the Retinoic Acid Pathway Medscape Education , September 2021 Go in depth with the retinoic acid pathway in the cell and learn how it can influence cellular activity.
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Facial and body care market is extremely competitive for a variety of reasons. Companies in the segment are forced to look for innovative solutions and compete on price, as the demand of the target customer group and the lack of product differentiation drive more severe rivalry and bring the product life cycle to a minimum. ODF and Dove are the major competitors in the facial care market, private brands and such companies as L'oreal, Nivea, and RoC, however, builds on competition in many specific product lines.

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Most Common Dermatologic Topics Published in Five High-Impact General Medical Journals, 1970–2012: Melanoma, Psoriasis, Herpes Simplex, Herpes Zoster, and Acne

Internists frequently diagnose herpes simplex, herpes zoster, and acne, which are also common dermatologic topics published. The authors conducted an independent search of the Thomson Reuters’ Science Citation Index for common dermatologic topics, limited to the period 1970 to 2012. The five most common dermatologic topics published in five high-impact general medical journals were melanoma, psoriasis, herpes simplex, herpes zoster, and acne.

General practitioners frequently encounter skin diseases and are accustomed to diagnosing the most common dermatologic conditions.

We sought to determine the most common dermatologic topics published in five high-impact general medical journals ( New England Journal of Medicine, The Lancet, the Journal of the American Medical Association, British Medical Journal (now The BMJ ), and Annals of Internal Medicine ).

We conducted an independent search of the Thomson Reuters’ Science Citation Index for common dermatologic topics, limited to the period 1970 to 2012.

Main Outcome Measure:

Total number of publications dealing with each dermatologic topic considered.

The five most common dermatologic topics published were melanoma, psoriasis, herpes simplex, herpes zoster, and acne. Melanoma and psoriasis were the top two dermatologic topics published in each journal except for Annals of Internal Medicine .

Conclusions:

Internists frequently diagnose herpes simplex, herpes zoster, and acne, which are also common dermatologic topics published. Although internists infrequently diagnose melanoma and psoriasis, they are major topics for general medical journals because of their increased community awareness, major advancements in therapeutic research, and their nondermatologic manifestations.

Introduction

Skin diseases are commonly encountered by general practitioners, and in today’s health care system, most patients are evaluated first by their primary care physician before seeing a dermatologist. It is estimated that 6% of primary care outpatient visits are skin-related, and 60% of cutaneous diagnoses are made by nondermatologists. 1 As the role of the general practitioner continues to grow, it remains imperative that these physicians are equipped to manage general dermatologic conditions.

To determine which skin diseases internists most commonly encounter, Feldman et al 2 analyzed the National Ambulatory Medical Care Survey data from 1990 to 1994. The top five dermatologic diagnoses made by internists during this period were dermatitis, bacterial skin infections, tinea, acne vulgaris, and herpes zoster. By highlighting these common diagnoses, it was anticipated that skin disease educational programs for internists would be tailored to these diseases. Moreover, this study demonstrated that diagnoses such as psoriasis, actinic keratosis, seborrheic keratosis, skin cancer, and benign tumors were commonly made by dermatologists but not by internists. These findings elucidated the overlapping yet differing role of the dermatologist and the internist, espousing the need for further communication and alliance in diagnosing a wide range of skin diseases.

The purpose of our study was to determine the most common dermatologic topics published from 1970 to 2012 in five high-impact general medical journals. We sought to analyze whether these journals, having the largest readership in medicine, targeted the common dermatologic diagnoses made by internists or focused on skin diseases more commonly diagnosed by dermatologists.

We analyzed data from the Thomson Reuters Science Citation Index. The five high-impact general medical journals we considered, based on the highest impact factors, were the New England Journal of Medicine (NEJM), The Lancet, the Journal of the American Medical Association (JAMA), British Medical Journal (now The BMJ ), and Annals of Internal Medicine. For each of these journals, we conducted an independent search for each of the dermatologic topics included in the study, limited to the years 1970 to 2012. The topics chosen were a modified list from the top dermatologic diagnoses made by internists and dermatologists 2 ( Table 1 ).

Total umber of articles for each dermatologic topic

Two independent reviewers analyzed search results to determine whether an article met the dermatologic topic under consideration. A consensus was achieved for all articles included. All types of publications (original research, case reports, review articles, meta-analyses, editorials, etc) were eligible for the study. If an article dealt with more than one possible topic, the topic that best fit the primary objective of the article was chosen. Topics without 20 or more papers in any of the 5 general medical journals were not mentioned.

A total of 2627 articles dealing with at least 1 of the 24 dermatologic topics mentioned in Table 1 were included in the study. From our combined data, the top 5 dermatologic topics published in the 5 high-impact general medical journals were melanoma (708 articles), psoriasis (455), herpes simplex (366), herpes zoster (253), and acne (165), as shown in Table 1 . The Lancet had the highest total number of dermatologic publications (744), followed by British Medical Journal (661), NEJM (630), JAMA (419), and Annals of Internal Medicine (173).

Melanoma was overwhelmingly the most common dermatologic topic in each of the journals except for Annals of Internal Medicine ( Figure 1 ). In NEJM, the second most common topic was psoriasis (100 articles), followed by herpes simplex (97) and herpes zoster (71). The other dermatologic topics were relatively uncommon in that journal. In The Lancet, the second most common topic was also psoriasis (144), followed by herpes simplex (102) and acne (49). There were also notable contributions to the dermatologic literature about herpes zoster (40), atopic dermatitis/eczema (40), urticaria (32), and abscess (28).

Frequency of common dermatologic topics mentioned in five high-impact general medical journals.

JAMA = Journal of the American Medical Association; NEJM = New England Journal of Medicine.

In JAMA, herpes simplex (with 68 articles) was the second most common dermatologic topic, followed by psoriasis (48) and herpes zoster (46). Acne (36), urticaria (30), and squamous cell carcinoma (22) followed in number of contributions. Melanoma (158) and psoriasis (134) were 2 greatly favored topics in the British Medical Journal. Herpes zoster (63), acne (60), and herpes simplex (56) made up the next highest proportion of topics, followed by abscess (35), urticaria (27), atopic dermatitis/eczema (26), and squamous cell carcinoma (22).

Annals of Internal Medicine was the only journal wherein melanoma (22) was not the most common dermatologic topic. In fact, melanoma was the fourth most prevalent. Preceding melanoma in prevalent articles was herpes simplex (43), herpes zoster (33), and psoriasis (29); see Figure 1 .

It has become customary for general practitioners to diagnose common skin conditions. For these physicians, primary sources for up-to-date information are general medical journals, namely the five high-impact journals ( NEJM, The Lancet, JAMA, British Medical Journal, and Annals of Internal Medicine ). By studying the prevalence of common dermatologic topics published in these journals, we attempted to provide insight into their emphasis on certain skin conditions.

Of the five high-impact general medical journals, we found that The Lancet and British Medical Journal, which have their foundation in the United Kingdom, published more articles on common dermatologic topics. In the United Kingdom, physicians must complete two years of foundation training and two years of core medical training before entering dermatology as a specialty. 3 This is in contrast to the US, where medical school graduates are required to complete only one year of internal medicine, general surgery, or pediatrics internship before entering dermatology residency. Perhaps in the United Kingdom, dermatology is integrated more with internal medicine, leading to a greater number of dermatologic publications in their general medical journals.

In our analysis, we found that herpes simplex, herpes zoster, and acne were three of the top five dermatologic topics published. This coincides with the fact that these topics were also among the top ten dermatologic diagnoses made by internists. 2 Melanoma and psoriasis, on the other hand, were the top two dermatologic topics published but are diagnoses rarely made by internists. 2

As mentioned by Feldman et al, 2 melanoma, despite being rarely diagnosed by internists, is important to internal medicine because of its serious nature. Some consider the early detection of melanoma, which has a 5-year survival rate of 98% if detected early and 15% with distant metastasis, 4 to be the responsibility of primary care physicians. 5 Furthermore, a “new era” of targeted and immune-based therapies for melanoma has been ushered in by recent advancements in melanoma research. 6 Many of these findings have gained publication in prestigious general medical journals. 7 – 9 It is not surprising, therefore, that melanoma was the most common dermatologic topic published in 4 of the 5 high-impact general medical journals we studied.

Psoriasis, like melanoma, is another diagnosis infrequently made by internists but was found in our study to be the second most common dermatologic topic published. With a prevalence of 1% to 3%, psoriasis is likely to be encountered by general practitioners. 10 Moreover, as a systemic inflammatory disease, psoriasis is compounded by psoriatic arthritis in 10% to 30% of cases. 10 Psoriasis has also been associated with a significantly increased risk of myocardial infarction, stroke, and peripheral vascular disease, possibly because of accelerated atherosclerosis in the setting of an inflammatory state. 11 These systemic manifestations, as well as the increasing prevalence of this dermatologic condition, make psoriasis a very relevant disease to internal medicine and the general medical journals. We acknowledge limitations in our study. Access to journal articles may have been limited by our university’s subscriptions, but all resources available were used to obtain articles. Certain articles that addressed multiple topics were categorized under one topic, considered the best fit by the reviewer. We referenced a study by Feldman et al, 2 who analyzed the National Ambulatory Medical Care Survey data from 1990 to 1994. Likely, diagnosing patterns of skin disease by internists may have changed since then, but to our knowledge, no similar analysis has yet been performed.

We believe our study achieved its primary purpose, to analyze the prevalence of common dermatologic topics published in high-impact general medical journals. We have demonstrated that certain dermatologic topics with increased relevance to internal medicine have greater numbers of publications. These findings are a testament to the value of these medical journals in providing relevant yet comprehensive information to general physicians, thus deserving the title of high-impact.

Acknowledgments

Kathleen Louden, ELS, of Louden Health Communications provided editorial assistance.

Disclosure Statement

Dr Wu received research funding from AbbVie, North Chicago, IL; Amgen Inc, Thousand Oaks, CA; Coherus Biosciences, Redwood City, CA; Eli Lilly, Indianapolis, IN; Merck, Whitehouse Station, NJ; and Pfizer, New York, NY, which were not directly related to this study. He is a consultant for AbbVie, North Chicago, IL; DUSA Pharmaceuticals Inc, Wilmington, MA; Eli Lilly, Indianapolis, IN; and Pfizer, New York, NY. Mr Choi and Mr Namavar have no conflicts of interest to disclose. No funding was received for this study.

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Removing NDIS support for period products robs independence and risks forced sterilisation, disability advocates warn

Topic: People With Disability

Companies like Modibodi make adaptable period undies that are used by some on the NDIS. ( Modibodi )

Women with disabilities are concerned that menstrual care could be ruled out of the NDIS as the scheme transitions to new rules.

It's unclear how long the transition will last.

What's next?

The federal government wants to pass its changes to the NDIS within a week.

Women with disabilities are worried they could lose access to essential period care as the NDIS transitions to new rules.

Menstrual items have been defined as "lifestyle-related", along with vapes, gambling and gaming PCs, in lists outlining what NDIS funding can and cannot be spent on during the transition.

But advocates insist products like adaptable period underwear and tampon inserters are necessary to ensure those with physical and intellectual disabilities can manage bleeding without hurting themselves.

Advocates are also concerned the change could lead to providers, carers and families opting for menstrual suppression methods like sterilisation to manage bleeding instead.

Adaptive undies can make managing periods much easier for those with disabilities.  ( Modibodi )

Fractured fingers, skin tears and TSS risk

Earlier this year, the federal government introduced legislation to make significant changes to the NDIS, which it is hoping to pass before next Thursday.

The changes include a new definition of what constitutes NDIS support, with any amendments yet to be negotiated with the states and territories.

"There are some people who are currently using their NDIS funding for menstrual products," said CEO of Women with Disability Australia Sophie Cusworth.

In a recent survey on the issue, the group heard from 180 women, with a majority saying their disability had a big impact on how they manage bleeding.

Women reported they need products like period undies or tampon insertion aids because inserting them by hand could lead to finger fractures for those with joint conditions or skin tearing, with some suggesting it's simply not possible due to lack of sensation.

Others cited worries about the risk of toxic shock syndrome — a rare condition that can result from tampons not being removed soon enough — if they could not access assistance aids.

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"[Some use] period underwear daily to manage incontinence, and for them, this meant that they could go to work or attend a mainstream school without requiring support with personal care" said Ms Cusworth.

"We're really concerned that the removal of access to these products might mean that people are losing independence, and that they are requiring regular support with changing the products and purchasing the products."

Women with Disability Australia is also warning the explicit exclusion of these items from the NDIS could result in the suppression of periods through medication or even forced sterilisation.

"We know that many people with disabilities are not given support and education to manage menstruation, and in many cases, have their menstruation suppressed without their free and informed consent," Ms Cusworth says.

Period products have been listed as not being covered by the NDIS in proposed government changes, but many say support from the scheme is essential. ( Getty Images: Jane Khom )

Cost barrier issue for community

El Gibbs from the Disability Advocacy Network Australia (DANA) said while period undies, tampons, inserters and pads might seem cheap, that isn't the case for the entire disability community.

"Half of people with disability live in poverty, and people with more severe disability who are likely to be on the NDIS pretty much live in poverty," she said.

Ms Gibbs said if this change is locked in it could have a big impact on women's independence.

"What is going to be the alternative, that they will pay a disability support worker to come over and support someone to, you know, use a tampon when that's not what they want to do?"

DANA's claims the lists themselves are too prescriptive, given how individual the needs of each NDIS participant are.

"It really doesn't give people the kind of flexibility and options and dignity that we were really hoping and that was the intention of the NDIS," said Ms Gibbs.

"I don't know about you, but I certainly never thought a bit of menstrual products that I used as being part of our lifestyle choice."

Tampon inserters can help those who might risk finger fractures from insertion.  ( 小草/Flickr CC by-nc-nd/2.0/ )

'Bleeding isn't a lifestyle choice'

Renee Carr, executive director of gender equity advocacy group Fair Agenda, said the idea that menstrual items are lifestyle products is laughable.

"Anyone who has had to deal with periods knows bleeding isn't a lifestyle choice," she said.

Ms Carr said access to appropriate period products is essential for dignity, health, hygiene and participation in the community.

"Managing your period can be difficult enough, without someone in a head office deciding that they have a better idea than you of what products work best — particularly if you're managing needs related to chronic pain, motor impairment, executive function, incontinence or limited mobility."

In 2018, this was a stance shared by Bill Shorten.

Talking about repealing the tampon tax, the then opposition leader now NDIS minister said using period products wasn't a lifestyle choice.

"There is no question that sanitary products aren't a luxury item, they are necessary for reproductive health and hygiene."

In response to questions from the ABC on these lists, Mr Shorten said he acknowledged there are a whole range of menstrual products used for disability-related issues.

"The Section 10 list of NDIS supports, what can and can't be paid for using NDIS funding, is still being finalised," he said.

"We will take this feedback onboard as part of the consultation on the clarification of NDIS supports."

The federal government has extended consultation for what will and will not be covered by a week, until August 25.

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Average number of skin care products used by women South Korea 2024

According to a survey among South Korean women on skin care products conducted in April 2024, 41.7 percent of respondents answered to use four to six different skin care products. The average amount of skin care products used among respondents amounted to roughly six products.

Average number of skin care products used among women in South Korea as of April 2024

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Life from a drop of rain: New research suggests rainwater helped form the first protocell walls

by University of Chicago

One of the major unanswered questions about the origin of life is how droplets of RNA floating around the primordial soup turned into the membrane-protected packets of life we call cells.

A new paper by engineers from the University of Chicago's Pritzker School of Molecular Engineering (UChicago PME), the University of Houston's Chemical Engineering Department, and biologists from the UChicago Chemistry Department, have proposed a solution.

In the paper, published in Science Advances , UChicago PME postdoctoral researcher Aman Agrawal and his co-authors—including UChicago PME Dean Emeritus Matthew Tirrell and Nobel Prize-winning biologist Jack Szostak—show how rainwater could have helped create a meshy wall around protocells 3.8 billion years ago, a critical step in the transition from tiny beads of RNA to every bacterium, plant, animal, and human that ever lived.

"This is a distinctive and novel observation," Tirrell said.

The research looks at "coacervate droplets"—naturally occurring compartments of complex molecules like proteins, lipids, and RNA. The droplets, which behave like drops of cooking oil in water, have long been eyed as a candidate for the first protocells. But there was a problem. It wasn't that these droplets couldn't exchange molecules between each other, a key step in evolution, the problem was that they did it too well, and too fast.

Any droplet containing a new, potentially useful pre-life mutation of RNA would exchange this RNA with the other RNA droplets within minutes, meaning they would quickly all be the same. There would be no differentiation and no competition—meaning no evolution.

And that means no life.

"If molecules continually exchange between droplets or between cells, then all the cells after a short while will look alike, and there will be no evolution because you are ending up with identical clones," Agrawal said.

Engineering a solution

Life is by nature interdisciplinary, so Szostak, the director of UChicago's Chicago Center for the Origins of Life, said it was natural to collaborate with both UChicago PME, UChicago's interdisciplinary school of molecular engineering, and the chemical engineering department at the University of Houston.

"Engineers have been studying the physical chemistry of these types of complexes—and polymer chemistry more generally—for a long time. It makes sense that there's expertise in the engineering school," Szostak said. "When we're looking at something like the origin of life , it's so complicated and there are so many parts that we need people to get involved who have any kind of relevant experience."

In the early 2000s, Szostak started looking at RNA as the first biological material to develop. It solved a problem that had long stymied researchers looking at DNA or proteins as the earliest molecules of life.

"It's like a chicken-egg problem. What came first?" Agrawal said. "DNA is the molecule which encodes information, but it cannot do any function. Proteins are the molecules which perform functions, but they don't encode any heritable information."

Researchers like Szostak theorized that RNA came first, "taking care of everything" in Agrawal's words, with proteins and DNA slowly evolving from it.

"RNA is a molecule which, like DNA, can encode information, but it also folds like proteins so that it can perform functions such as catalysis as well," Agrawal said.

RNA was a likely candidate for the first biological material. Coacervate droplets were likely candidates for the first protocells. Coacervate droplets containing early forms of RNA seemed a natural next step.

That is until Szostak poured cold water on this theory, publishing a paper in 2014 showing that RNA in coacervate droplets exchanged too rapidly.

"You can make all kinds of droplets of different types of coacervates, but they don't maintain their separate identity. They tend to exchange their RNA content too rapidly. That's been a long-standing problem," Szostak said.

"What we showed in this new paper is that you can overcome at least part of that problem by transferring these coacervate droplets into distilled water—for example, rainwater or freshwater of any type—and they get a sort of tough skin around the droplets that restricts them from exchanging RNA content."

'A spontaneous combustion of ideas'

Agrawal started transferring coacervate droplets into distilled water during his Ph.D. research at the University of Houston, studying their behavior under an electric field. At this point, the research had nothing to do with the origin of life, just studying the fascinating material from an engineering perspective.

"Engineers, particularly Chemical and Materials, have good knowledge of how to manipulate material properties such as interfacial tension, role of charged polymers, salt, pH control, etc.," said University of Houston Prof. Alamgir Karim, Agrawal's former thesis advisor and a senior co-author of the new paper. "These are all key aspects of the world popularly known as 'complex fluids'—think shampoo and liquid soap."

Agrawal wanted to study other fundamental properties of coacervates during his Ph.D. It wasn't Karim's area of study, but Karim had worked decades earlier at the University of Minnesota under one of the world's top experts—Tirrell, who later became founding dean of the UChicago Pritzker School of Molecular Engineering.

During a lunch with Agrawal and Karim, Tirrell brought up how the research into the effects of distilled water on coacervate droplets might relate to the origin of life on Earth. Tirrell asked where distilled water would have existed 3.8 billion years ago.

"I spontaneously said 'rainwater!' His eyes lit up and he was very excited at the suggestion," Karim said. "So, you can say it was a spontaneous combustion of ideas or ideation!"

Tirrell brought Agrawal's distilled water research to Szostak, who had recently joined the University of Chicago to lead what was then called the Origins of Life Initiative. He posed the same question he had asked Karim.

"I said to him, 'Where do you think distilled water could come from in a prebiotic world?'" Tirrell recalled. "And Jack said exactly what I hoped he would say, which was rain."

Working with RNA samples from Szostak, Agrawal found that transferring coacervate droplets into distilled water increased the time scale of RNA exchange—from mere minutes to several days. This was long enough for mutation, competition, and evolution.

"If you have protocell populations that are unstable, they will exchange their genetic material with each other and become clones. There is no possibility of Darwinian evolution," Agrawal said. "But if they stabilize against exchange so that they store their genetic information well enough, at least for several days, so that the mutations can happen in their genetic sequences, then a population can evolve."

Rain, checked

Initially, Agrawal experimented with deionized water, which is purified under lab conditions. "This prompted the reviewers of the journal who then asked what would happen if the prebiotic rainwater was very acidic," he said.

Commercial lab water is free from all contaminants, has no salt, and lives with a neutral pH perfectly balanced between base and acid. In short, it's about as far from real-world conditions as a material can get. They needed to work with a material more like actual rain.

What's more like rain than rain?

"We simply collected water from rain in Houston and tested the stability of our droplets in it, just to make sure what we are reporting is accurate," Agrawal said.

In tests with the actual rainwater and with lab water modified to mimic the acidity of rainwater, they found the same results. The meshy walls formed, creating the conditions that could have led to life.

The chemical composition of the rain falling over Houston in the 2020s is not the rain that would have fallen 750 million years after the Earth formed, and the same can be said for the model protocell system Agrawal tested.

The new paper proves that this approach of building a meshy wall around protocells is possible and can work together to compartmentalize the molecules of life, putting researchers closer than ever to finding the right set of chemical and environmental conditions that allow protocells to evolve.

"The molecules we used to build these protocells are just models until more suitable molecules can be found as substitutes," Agrawal said. "While the chemistry would be a little bit different, the physics will remain the same."

Journal information: Science Advances

Provided by University of Chicago

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