Constitutive Skin Research Articles

Analysis of Skin Color Variation using CIELAB Index: An Empirical Study from Delhi, India

Skin color is a conspicuous trait regulated by complex metabolic processes and its significant diversity among Indian populations is quite remarkable making it an ideal choice for dermatological investigation. To elucidate skin pigment variation with respect to age, we studied 714 healthy individuals (aged 20-70 years) using CIELAB system. Skin reflectance was measured from the volar surface of upper arm using DSM II ColorMeter (Cortex Technology, Hadsund, Denmark) among population of Delhi, India to provide CIELAB color space values, L* (light/dark), a* (red/green), and b* (yellow/blue) followed by statistical analysis to examine the correlation between age and gender on skin on constitutive skin pigmentation. The studied parameters were observed to vary widely {L* (Range: 24.98-51.62, M=38.66, SD=4.41), a* (Range: 4.61-17.16, M=10.18, SD=2.03), and b* (Range: 20.16-34.83, M=28.93, SD=2.30)} across all age groups. ANOVA results suggest a statistically significant effect of age on skin lightness {F(4,709)=124.1332, p<0.001}, redness {F(4,709)=20.0594, p<0.001} and yellowness {F(4,709)=95.1434, p<0.001}. Positive correlation was observed between age and both hue (ho) {r(712)=0.9027, p<0.001} and chroma (C) {r(712)=0.9224, p<0.001}. Significant effects of gender were noticed on skin lightness among all age groups, along with skin redness below the age of 40 years (p<0.001). Notable color differences (∆Ε∗ab) were witnessed among males and females across all age groups in the studied population. The age group 21-30 years was found to have the highest ∆Ε∗ab value (3.5987), followed by 51-60 years (2.98), 31-40 years (2.5579), 61-70 years (2.1837), and 41-50 years (1.6639). We would like to highlight that skin lightness, redness, and yellowness differs significantly with age. Females were observed to be lighter in color as compared to males across all age groups. The findings of the current study would provide better understanding of skin color variation among Indian population.

Solar exposure, the melanocyte and melanoma: Survival pathways and molecular mechanisms.

The keratinocyte and the melanocyte, the main cellular constituents of the epidermis, are two very different cell types. Despite their different origins and functionality, they come together in the skin, synergistically, to function as a unit to control the adverse effects of solar exposure. The most significant element in this protective process is the ability of the melanocyte to produce melanin. This pigmented polymer is responsible for constitutive skin colour that plays a part in our identity as human individuals but more importantly, provides a tanning response. A change in pigmentation that provides both an immediate and prolonged protective effect from the damaging components of solar radiation. The melanocortin 1 receptor, a cell surface receptor on the melanocyte, receives paracrine stimulation in the form of hormonal communication from the keratinocyte, initiating a series of intracellular molecular interactions in the melanocyte, eventually involving transcription factors in the nucleus, most notably the microphthalmia-associated transcription factor, resulting in upregulation of enzymatic production of melanin and finally, its transfer back to the keratinocyte. The melanocortin 1 receptor is highly polymorphic and unfortunately this results in the Caucasians’ having constitutionally fairer skin combined with an incomplete tanning response, resulting in a higher susceptibility to skin cancer. The melanocyte is a relatively long-lived cell and over its extended life span can accumulate a series of mutational events. With malignant transition to melanoma this oncogenic baggage, when combined with antiapoptotic machinery that helps melanocyte survival, resulting in relatively rapid progression of the malignant process and contributing to its resistance to therapeutics.

Results of longitudinal Nutri-D study: factors influencing winter and summer vitamin D status in a Caucasian population.

Inadequate vitamin D status is a worldwide public health issue. In humans, vitamin D status is affected by diet, and even more by exposure to ultraviolet B (UVB) light and consequential endogenous synthesis. Various personal and environmental factors influence endogenous synthesis. Factors affecting vitamin D status were investigated in a prospective longitudinal cohort study with a summer and winter observation period. The final sample included 292 adults, of those 111 (38%) males and 181 (62%) females, with a mean age of 38.2 (±11.8) years from Slovenia who were not supplementing vitamin D. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured in both periods; vitamin D intake, self-reported body mass index (BMI), and protective behaviors against sun were also recorded. Other measured parameters included measurements of constitutive skin color using the objective individual typology angle (ITA), and difference in the melanin index (ΔMI) for assessment of objective sun exposure. In winter a high prevalence (63.4%) of insufficient vitamin D status (< 50 nmoL/L) was observed with higher odds ratios (OR) for insufficiency in those with a higher BMI and light ITA. During summer, insufficiency prevalence was low (5.5%), but half of the participants (50.0%) had suboptimal 25(OH)D concentration (< 75 nmol/L). In summer OR for suboptimal status were higher in those with obesity, lower ΔMI, light ITA, low vitamin D intake, and protective clothing behaviors. Using a series of measures, we showed that vitamin D status is hugely affected by several personal factors such as BMI, ITA, vitamin D intake, ΔMI, and protective behavior against the sun. This conclusion questions the usefulness of generalized population-level recommendations since personal factors are a major predictor of vitamin D status.

Melanin's Journey from Melanocytes to Keratinocytes: Uncovering the Molecular Mechanisms of Melanin Transfer and Processing.

Skin pigmentation ensures efficient photoprotection and relies on the pigment melanin, which is produced by epidermal melanocytes and transferred to surrounding keratinocytes. While the molecular mechanisms of melanin synthesis and transport in melanocytes are now well characterized, much less is known about melanin transfer and processing within keratinocytes. Over the past few decades, distinct models have been proposed to explain how melanin transfer occurs at the cellular and molecular levels. However, this remains a debated topic, as up to four different models have been proposed, with evidence presented supporting each. Here, we review the current knowledge on the regulation of melanin exocytosis, internalization, processing, and polarization. Regarding the different transfer models, we discuss how these might co-exist to regulate skin pigmentation under different conditions, i.e., constitutive and facultative skin pigmentation or physiological and pathological conditions. Moreover, we discuss recent evidence that sheds light on the regulation of melanin exocytosis by melanocytes and internalization by keratinocytes, as well as how melanin is stored within these cells in a compartment that we propose be named the melanokerasome. Finally, we review the state of the art on the molecular mechanisms that lead to melanokerasome positioning above the nuclei of keratinocytes, forming supranuclear caps that shield the nuclear DNA from UV radiation. Thus, we provide a comprehensive overview of the current knowledge on the molecular mechanisms regulating skin pigmentation, from melanin exocytosis by melanocytes and internalization by keratinocytes to processing and polarization within keratinocytes. A better knowledge of these molecular mechanisms will clarify long-lasting questions in the field that are crucial for the understanding of skin pigmentation and can shed light on fundamental aspects of organelle biology. Ultimately, this knowledge can lead to novel therapeutic strategies to treat hypo- or hyper-pigmentation disorders, which have a high socio-economic burden on patients and healthcare systems worldwide, as well as cosmetic applications.

Seasonal Tanning-Induced Increases in Skin Pigmentation Do Not Affect Nitric Oxide-Mediated Vasodilation of the Cutaneous Microvasculature

Acute ultraviolet radiation (UVR) exposure reduces nitric oxide (NO)-dependent cutaneous vasodilation. Additionally, increased constitutive skin melanin concentrations are associated with reduced NO-dependent cutaneous vasodilation. However, the impact of seasonal tanning-induced increases in skin melanin concentration on NO-dependent cutaneous vasodilation has not been investigated. PURPOSE: To investigate the effect of seasonal tanning-induced increases in skin melanin on the NO-dependent cutaneous vasodilation response to local heating. We hypothesized that NO-dependent cutaneous vasodilation would be reduced in tanned skin relative to untanned skin. METHODS: Three intradermal microdialysis fibers were placed in the ventral upper arm (least sun exposed), ventral forearm (moderately sun exposed), and dorsal forearm (most sun exposed) of seven adults (33 ± 14 yrs; 4M/3F) with light-to-moderate constitutive skin pigmentation. Differences in sun exposure among the sites was confirmed using the melanin-index (M-index; an index of skin pigmentation), measured via skin reflectance spectrophotometry. Lactated Ringer’s solution was perfused through the microdialysis fibers while local heating to 42°C induced cutaneous vasodilation. After attaining a stable plateau in cutaneous blood flow, 15mM NG-nitro-L-arginine methyl ester (L-NAME; NO synthase inhibitor) was perfused at all sites to quantify NO-mediated vasodilation. Red cell flux was measured using laser-Doppler flowmetry (LDF). Cutaneous vascular conductance (CVC=LDF/mean arterial pressure) was calculated for each phase of the local heating response (i.e., baseline, initial peak, local heating plateau, post L-NAME plateau) and expressed as percent maximum (%CVCmax; 28mM sodium nitroprusside + 43°C local heating). RESULTS: M-index was highest (i.e., skin pigmentation was darkest) in the dorsal forearm (50.5 ± 11.8 a.u.) compared to the ventral forearm (37.5 ± 7.4 a.u.; p ≤ 0.03) and upper arm (30.2 ± 5.1 a.u.; p ≤ 0.001). There were no baseline (p ≥ 0.37), initial peak (p ≥ 0.22), post L-NAME plateau (p ≥ 0.12), or maximal CVC (p ≥ 0.23) differences among the three sites. Likewise, the magnitude of the local heating plateau was not different among the three sites (dorsal: 88±17%; ventral: 81±20%; upper: 90±12%; p ≥ 0.16), nor was NO-mediated vasodilation (dorsal: 59±15%; ventral: 54±13%; upper: 55±11.0%; p ≥ 0.79). CONCLUSION: These data suggest that, in contrast to the effects of acute UVR exposure or a constitutively dark skin pigmentation, seasonal tanning-induced increases in skin pigmentation do not alter NO-dependent cutaneous vasodilation responses to local heating. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A Cross-Sectional Assessment of Quantitative Epidermal Melanin and Erythema Indices among North Indians.

Remarkable diversity of skin tones among Indians ranging from pale pinkish to dark brown appears to be an ideal choice for the assessment of skin pigment variation. The present study was designed to assess the variation observed in melanin and erythema indices among north Indians. Skin reflectance data (n = 574) was collected from six diverse populations of north India using DermaSpectrometer (DSM II ColorMeter) followed by statistical analysis to investigate the impact of geographical location and gender on constitutive skin pigmentation. The melanin index (MI) varied between 17.93 and 56.92 (Mean (M) = 35.80 ± 6.26) whereas the erythema index (EI) varied between 4.92 and 18.82 (M = 10.48 ± 2.68). MI and EI of females were found to be significantly lower than males (P < 0.001). Geographical location exhibited a significant association with MI and EI (P < 0.001). Furthermore, we have noted a positive correlation between MI and EI (P < 0.001). The study has refined our understanding of skin pigmentation variation among north Indians in terms of significant association with geographical location {MI: F (5,568) = 31.07, P < 0.001; EI: F (5,568) = 73.37, P < 0.001} and gender {MI: t (386) = -4.06, P < 0.001; EI: t (386) = -11.96, P < 0.001} and rendered opportunities for further studies.

The Eumelanin Human Skin Colour Scale: a proof-of-concept study.

At present there is no standard nomenclature for describing the diversity of human constitutive skin colour. To develop a standard nomenclature to describe human constitutive skin colour. Monthly focus group discussions were carried out among a multidisciplinary group of specialists over a 7-month period. Topics covered were (i) limitations and unmet needs of current nomenclature(s) pertaining to human cutaneous diversity, (ii) practical considerations about the function and role of any proposed nomenclature pertaining to human cutaneous diversity, (iii) review of the cellular basis and current molecular genetic understanding of variation in human skin pigmentation and (iv) in vivo methods to evaluate human skin pigmentation. In addition, a preliminary review of the published literature was undertaken to collate data on published skin reflectance measurements, notably melanin index values for well-referenced human populations. We developed a five-point scale to describe the full spectrum of human constitutive skin colour, termed the Eumelanin Human Skin Colour Scale. The nomenclature of the scale uses eumelanin, the dominant chromophore of human skin, as a central descriptive word. The categories of the scale (nomenclature and melanin index values) are eumelanin low (EML), < 25; eumelanin intermediate low (EMIL), 25 to < 50; eumelanin intermediate (EMI), 50 to < 75; eumelanin intermediate high (EMIH), 75 to < 100; and eumelanin high (EH), ≥ 100. The Eumelanin Human Skin Colour Scale enables the complete range of human constitutive skin colour to be described in an objective, equitable and understandable manner. In future, this scale can be used as the basis for developing other scales that address the specific functional aspects of human skin, such as response to ultraviolet radiation.

Sun Exposure Is Associated with Reduced Breast Cancer Risk among Women Living in the Caribbean: The Atabey Study in Puerto Rico.

Though inconsistent, there is evidence that sun exposure is associated with reduced breast cancer risk. Previous studies have been conducted in geographical regions with seasonal variation in UV radiation, including periods of low to no exposure, and among participants mostly of European descent. Puerto Rico has no significant seasonal fluctuation, with continuous exposure to very high UV radiation. We conducted a population-based case-control study of breast cancer among women in metropolitan San Juan, Puerto Rico, examining a cumulative sun exposure index (SEI) based on a comparison of reflectance of sun-exposed and non-exposed skin. A chromameter was used to measure skin reflectance and estimate the difference between constitutive (unexposed) and facultative (exposed) skin pigmentation in 307 cases and 328 controls. Breast cancer risk factors were ascertained with interviewer-administered questionnaires. OR and 95% confidence intervals (CI) were estimated with unconditional logistic regression. Adjusted breast cancer odds were lower for the highest tertile of the SEI (ORadj = 0.47; 95% CI, 0.29-0.74). Results were similar within strata of estrogen receptor status. In analyses stratified by constitutive skin pigmentation, among participants with darker skin color, breast cancer risk was lower with more sun exposure (ORadj = 0.33; 95% CI, 0.16-0.70). We found lower risk of breast cancer associated with greater sun exposure in a population living with high, continuous sun exposure. This beneficial finding should be placed in the context of other effects of sun exposure. Sun exposure is a modifiable factor that may contribute, directly or indirectly, to lower breast cancer risk.

Low vitamin D in dark-skinned immigrants is mainly due to clothing habits and low UVR exposure: a Danish observational study.

Low 25-hydroxyvitamin D3 (25(OH)D) among dark-pigmented persons has been observed. To elucidate the reason for this we examined sun behaviour, sun-exposed body area, solar UVR exposure and 25(OH)D levels in immigrants with dark pigmented skin and Danes with light pigmented skin. Clothing, sun behaviour, and diet were recorded daily during a Danish summer season (93 analysed days). Erythema-weighted UVR doses were measured by personal electronic UVR dosimeters (with erythema response, measurement every 5th second) and 25(OH)D was measured in 72 participants (33 dark-skinned and 39 light-skinned). The immigrants exposed 28% less skin area, received 70% less UVR dose, and had 71% less 25(OH)D increase during the summer. The UVR reactivity (Δ25(OH)D per joule accumulated UVR dose) was similar (P = 0.62) among the immigrants (0.53nmoll-1J-1) and the Danes (0.63nmoll-1J-1). In the groups combined, 25(OH)D levels after summer were mainly influenced by UVR dose to exposed skin (28.8%) and 25(OH)D start level (27.9%). Height and measured constitutive skin pigmentation were of minor influence: 3.5% and 3.2%, respectively. Sun exposure and clothing habits were the main reasons for lower 25(OH)D level after summer in the darker immigrants, as both groups had similar UVR reactivity.

Blue Lagoon Algae Improve Uneven Skin Pigmentation: Results from in vitro Studies and from a Monocentric, Randomized, Double-Blind, Vehicle-Controlled, Split-Face Study

Introduction: Bathing in the Blue Lagoon (BL) in Iceland benefits patients with psoriasis. Accordingly, the BL water contains algae with biological activities that improve skin barrier function and affect T-cell responses relevant for psoriasis. Bathing in the BL is also becoming increasingly popular among healthy individuals and anecdotal evidence suggests positive effects on uneven skin pigmentation. Objective: The aim of the study was to address the impact of BL algae on skin pigmentation. Methods: In this work, in vitro gene expression studies in melanocytes and a noninvasive in vivo study were conducted. Results: We here report that normal human epidermal melanocytes, which had been treated with nontoxic concentrations of BL algae, show a significantly reduced expression of α melanocyte-stimulating hormone-induced expression of genes important for melanin synthesis, such as tyrosinase, tyrosinase-related protein 1, dopachrome tautomerase, melan A protein, and pre-melanosome protein. This in vitro observation prompted us to conduct a randomized, double-blind, intra-individual, comparative split-face in vivo study, in which 60 volunteers with pre-existing facial pigment spots were treated twice daily with a BL algae containing serum or a vehicle control. We found that constitutive skin pigmentation as determined by colorimetry (individual typology angle and luminescence) did not differ significantly between vehicle- and serum-treated skin sites. In marked contrast, digital photography under cross-polarized lighting and RBX technology (VISIA CR) revealed that the number of pigment spots in the serum-treated face decreased significantly compared to the vehicle-treated side. Conclusion: Thus, BL algae can affect human melanocyte function in vitro and reduce uneven facial skin pigmentation in vivo.

Representation in Figures Depicting Penile Pathology in Urologic Textbooks

To investigate whether penile pathologies are presented diversely in urologic textbooks and identify areas where more diverse presentation is warranted. Photographic depictions of penile pathologies in 9 urologic textbooks were assigned a Fitzpatrick skin phototype and constitutive skin color. Fitzpatrick skin phototypes ranged from I to VI, and constitutive skin colors were light, fair, medium, and dark. Fitzpatrick skin phototypes I-III were deemed nonskin of color, and IV-VI considered skin of color. Figures were classified based on pathology presented: infectious benign or sexually transmitted infection (STI), noninfectious benign, or malignant. Chi-square and odds ratios were used to compare skin color ranges across pathologic categories and determine where a figure depicting skin color would most likely be encountered. Within 116 figures meeting inclusion criteria, 15 (51.7%) infectious/STI pathologies displayed skin of color, while 10 (27.8%) noninfectious benign and 7 (13.7%) malignant pathologies displayed skin of color. Within 85 diagnostic images, 15 (51.7%) images of infections/STIs, 10 (28.6%) noninfectious benign, and 4 (19.0%) malignant pathologies presented skin of color (P < 0.01). Overall, images of patients with skin of color were more likely depictions of infections/STIs than any other pathology (P < .001, OR = 2.26). There is a lack of depictions of malignant and noninfectious benign penile pathology on the skin of color. This may contribute to continued disparities in the diagnosis and treatment of penile pathologies.

The continuous development of a complete and objective automatic grading system of facial signs from selfie pictures: Asian validation study and application to women of three ethnic origins, differently aged.

To evaluate the capacity of the automatic detection system to accurately grade, from smartphones' selfie pictures, the severity of seven new facial signs added to the nine previously integrated. A two-step approach was conducted: first, to check on 112 Korean women, how the AI-based automatic grading system may correlate with dermatological assessments, taken as reference; second, to confirm on 1140 women of three ancestries (African, Asian, and Caucasian) the relevance of the newly input facial signs. The sixteen specific Asian facial signs, detected automatically, were found significantly (P<.0001) highly correlated with the clinical evaluations made by two Korean dermatologists (wrinkles: r=.90; sagging: r=.75-.95; vascular: r=.85; pores: r=.60; pigmentation: r=.50-.80). When applied at a larger scale on women of different ethnicities, new signs were found of good accuracy and reproducibility, albeit depending on ethnicity. Due to contrast with the innate skin complexion, the facial signs dealing with skin pigmentation were found of a much higher relevance among Asian women than African or Caucasian women. The automatic gradings were even found of a slightly higher accuracy than the clinical gradings. The previously used automatic grading system is now completed by adding new facial signs apt at being detected. The continuous development is now integrating some limitations with regard to the constitutive skin complexion of the self-pictured subjects. Presenting reproducible assessments, highly correlated with medical grading, this system could change tremendously clinical researches, like in epidemiological studies, where it offers an easy, fast, affordable, and confidential approach in the objective quantification of facial signs.

Subjective and objective skin colour of a farmworker group in the Limpopo Province, South Africa.

Farmworkers in the Limpopo Province, South Africa, are at risk of excessive exposure to solar ultraviolet radiation (sUVR) due to both their work and the sUVR environment in the geographic area. However, the natural protection provided by this group's skin against sUVR has not been quantified. The aim of this study was to evaluate the subjective and objective skin colour of a group of farmworkers in order to classify the natural photoprotection provided by melanin and to evaluate the different measurement methods. Skin colour was established by using the subjective Fitzpatrick skin phototype system (FST) questionnaire and two objective methods, namely the individual typology angle (ITA°) and melanin index (MI). A total of 71 farmworkers participated in the study. Black Africans tended to perceive their skin to be lighter than objectively measured, potentially due to cultural factors. The constitutive skin colour of most farmworkers was objectively classified in the FST V/brown group. Significant differences were found between the ITA° and MI of sun-exposed (constitutive) and non-sun-exposed (facultative) skin in Black African and White farmworkers. A strong correlation was found between ITA° and MI on different anatomical positions indicating both methods are appropriate to determine skin colour in deeply pigmented skin. The evaluation of skin colour with the use of both subjective and objective methods may be used to design an effective photoprotection programme for farmworkers in the Limpopo Province.

Melanogenic Difference Consideration in Ethnic Skin Type: A Balance Approach Between Skin Brightening Applications and Beneficial Sun Exposure.

Human skin demonstrates a striking variation in tone and color that is evident among multiple demographic populations. Such characteristics are determined predominantly by the expression of the genes controlling the quantity and quality of melanin, which can alter significantly due to the presence of small nucleotide polymorphism affecting various steps of the melanogenesis process and generally linked to the lighter skin phenotypes. Genetically determined, constitutive skin color is additionally complemented by the facultative melanogenesis and tanning responses; with high levels of melanin and melanogenic factors broadly recognized to have a protective effect against the UVR-induced molecular damage in darker skin. Long-term sun exposure, together with a genetic makeup responsible for the ability to tan or the activity of constitutive melanogenic factors, triggers defects in pigmentation across all ethnic skin types. However, sun exposure also has well documented beneficial effects that manifest at both skin homeostasis and the systemic level, such as synthesis of vitamin D, which is thought to be less efficient in the presence of high levels of melanin or potentially linked to the polymorphism in the genes responsible for skin darkening triggered by UVR. In this review, we discuss melanogenesis in a context of constitutive pigmentation, defined by gene polymorphism in ethnic skin types, and facultative pigmentation that is not only associated with the capacity to protect the skin against photo-damage but could also have an impact on vitamin D synthesis through gene polymorphism. Modulating the activities of melanogenic genes, with the focus on the markers specifically altered by polymorphism combined with differential requirements of sun exposure in ethnic skin types, could enhance the applications of already existing skin brightening factors and provide a novel approach toward improved skin tone and health in personalized skincare.

Feeling the heat: Extreme temperatures compromise constitutive innate humoral immunity and skin color in a desert dwelling lizard.

Environmental temperature, particularly in habitats with extreme temperature fluctuations, may shape selection pressures on life history traits. Especially in ectotherms, temperature affects performance, physiology, and in some species, skin color. Skin color can be a sexual ornament signaling the bearer's ability to resist infections, when only high-quality individuals are able to invest both in high immune defense and elaborate ornament expression. However, how the information content of these sexual traits may vary with environmental conditions has been less studied. Dickerson's collared lizard (Crotaphytus dickersonae) males are blue and have a black and white collar. This conspicuous coloration signals performance and immune response, and is related to body temperature. Here, by maintaining males at higher, lower, and mean environmental temperatures we evaluated whether temperature variation influences color and constitutive innate humoral immunity (agglutination and lysis titers, estimated through hemolysis-hemagglutination assays), and whether extreme temperatures impose trade-offs between color and humoral immunity. We found that at low and high temperature treatments males had lower agglutination and lysis titers, and at low temperature, blue chroma from the dorsum declined and males became greener. Interestingly, at low and control temperature treatments, agglutination titer and blue coloration were positively correlated, whereas high temperatures revealed a trade-off between increasing agglutination titers and displaying bluer skin color. Our results suggest that in the Dickerson collared lizard even short-term variation of environmental temperature affects performance of constitutive innate humoral immunity and the brilliant blue skin color. Particularly, high temperatures may compromise some components of male's immunity and sexual signaling.

Evaluating age-related changes of some facial signs among men of four different ethnic groups.

The alterations of some facial characteristics, with age, in men of different ethnic groups are a scarcely studied topic. To illustrate and grade, among men of four different ethnic descents (Asians, African-Americans, Caucasians, Indians), aged 18-80year, the changes in the severity of some facial signs occurring with age. Digital Photographs (full face, profile, 45°) of 1058 subjects were taken under standard conditions of lightning. These allowed us to zoom in on 15-20 different facial signs on all subjects. Their observations by 15 trained experts, under calibrated screens, allowed these signs to be graded, with the help of four referential skin Atlases, specific to the gender and ethnic groups studied. Most facial signs show a rather regular increase with age, with different kinetics according to the ethnic group. The major changes, in all four ethnic groups, mostly concern skin structural alterations (wrinkles, neck sagging or texture). The changes in the severity of some wrinkles (forehead, inter-ocular…) may be viewed as ethnic signatures. The modifications in pigmentation disorders seem more closely linked to the constitutive skin pigmentation (photo-types), among which pigmentary spots are confirmed as a more specific Asian trait. Men of four different ethnic origins present different and ethnic-related facial alterations with increasing age, of different amplitudes.

The effect of pre-phototest sun exposure on minimal erythema dose and minimal melanogenic dose among skin phototypes III, IV and V.

Ethnicity, skin phototype and colour influenced minimal erythema dose (MED). Sun exposure has been postulated to increase MED. We determined immediate pigment darkening dose to UVA (IPDDA), MED and minimal melanogenic dose (MMD) for UVB and UVA, and investigated factors affecting these doses. Skin phototype was determined using Fitzpatrick phototype quiz, DSMII ColorMeter measured skin colours, sun exposure quantified using an index (SEI) and phototest performed with MEDlight-Multitester. A total of 167 healthy volunteers participated. There were 110 (66%) females and 56 (34%) males; 124 (74.7%) were Malay, 27 (16.3%) Chinese and 14 (8.4%) Indians. One hundred and nine (65.7%) skin phototype IV, 30 (18.1%) phototype III and 27 (16.3%) phototype V. IPDDA ranges from 6±1.5-5.7±1.4J/cm2 . MED-UVB were 96.9±17.6, 124±29.3 and 118.6±27.4mJ/cm2 for phototype III, IV and V, respectively. All MED-UVA were outside the tested dose range of 3.6-11J/cm2 . MMD-UVB were 106±18.2, 134±25.6 and 136±31.1mJ/cm2 while MMD-UVA were 4.1±4.1, 4.9±3.8 and 5.7±3.7J/cm2 respectively for phototypes III, IV and V. MED-UVB, MMD-UVB and MMD-UVA did not depend on skin phototype. Facultative skin whiteness (L*), erythema (E) and melanin content (M) correlated significantly with MED-UVB while constitutive skin colours were significant for L*, yellowness (b*), E and M. Sun exposure did not significantly correlate with MED-UVB and MMDs, however, an inverse relationship with MED-UVB was demonstrated. Minimal erythema doses in our cohort were slightly different from other regional countries. Constitutive and facultative skin whiteness, erythema and melanin content correlated with MED. There was no association between skin phototype and sun exposure with MED or MMD.

Photoprotection in specific populations: Children and people of color

Improved education on appropriate photoprotection in children is vital. Photoprotection for these individuals should include seeking shade, the use of physical agents (clothing, hat, sunglasses), and application of sunscreens on exposed areas. Avoidance of the use of tanning beds is an important component of education for teenagers. Ultraviolet radiation exposure induces DNA damage and photoaging in all skin types, including people of color. The extent of such damage is inversely related to constitutive skin pigmentation. Therefore, personalized photoprotection recommendations concerning skin cancer risk factors, desired treatment outcomes, health needs (eg, vitamin D), and photoaging based on the needs and preferences of the patient are essential. It is clear that additional research is needed on optimal levels of protection against ultraviolet radiation for people of color.

Defining "intermittent UVR exposure".

Cutaneous malignant melanoma (CMM) has been associated with "intermittent UVR exposure", which in previous studies has mainly been assessed by retrospective questionnaire data. Further, there is no uniform definition of the term "intermittent UVR exposure". We aimed to define and quantify "intermittent UVR exposure" by an objective measure. A broad study population of adults and children had data collected during a summer period. Data were personal UVR dosimetry measurements, from which the number of "intermittent days" was derived, sun behaviour diaries and retrospective questionnaires. Two definitions of intermittent UVR exposure were tested: (1) days when UVR dose exceeded 3 times individual average daily UVR dose, and (2) days when UVR dose exceeded individual constitutive skin type. Measures of nevi and lentigines were used as surrogates for CMM. Using the first definition based solely on UVR dosimetry data we found 1241 "intermittent days" out of a total of 17 277 days (7.2%) among 148 participants. The numbers for nevi and lentigo density were significantly predicted by the number of intermittent days (R(2) = 0.15 and R(2) = 0.40, p < 0.001). The corresponding numbers for prediction of nevi and lentigo density by retrospective questionnaire data was lower (R(2) = 0.11, R(2) = 0.26, p < 0.001). We introduce a well-defined objective measure of intermittent UVR exposure. This measure may provide a better prediction of solar skin damage and CMM than retrospective questionnaire data.

Selected gene polymorphisms effect on skin and hair pigmentation in Polish children at the prepubertal age.

Background: Human pigmentation, similarly as many other biological features, changes in the course of post-natal ontogenesis, while in case of hair, pigmentation changes are more distinctive than in the skin or the iris. It is therefore extremely important to identify the genes, involved in the constitution of human pigmentation features at various stages of ontogenesis. Results of this type of analyses are of high practical significance in forensic study because they enable to create mathematical tools, allowing for prediction of the pigmentation phenotype, based on DNA studies. Aim: The objective of the investigation was finding out whether the genes, associated with pigmentation of adult subjects, differentiated in any way the newly forming pigmentation phenotype in Polish prepubertal children. Material and methods: The study encompassed Polish children, aged 7 to 10 years, without any abnormalities in skin or hair pigmentation. A total of 245 children were examined. Constitutive skin pigmentation according to skin melanin index (SMI) was evaluated, using a dermaspectrometer, and classified into three groups based on the reference values of 25 and 75 percentile for Polish children. Hair colors were evaluated by means of the descriptive Fischer-Saller scale and classified by a division of color variants (as accepted in that scale) (light blonde, blonde, dark blonde, brown and dark brown). In saliva samples, collected from the children, five (5) single nucleotide polymorphisms were identified: SNPs: rs1800401 (OCA2-15q11.2-q12), rs35264875 (TPCN2-11q13.3), rs16891982 (SLC45A2-5p13.2), rs12913832 (HERC2-15q13) and rs1805007 (MC1R-16q24.3). An association between each allele of verified genotype and skin and hair color phenotypes was assessed, using the z-statistic and associated p-value. The quality of classifiers was evaluated by 10-fold stratified cross-validation and was characterized by the area under the receiver operating characteristic curve (AUC). Results: Light skin pigmentation phenotype (SMI<25 percentile) was associated with rs1805007 (MC1R) (allelic OR=3.95; 95% Cl:1.20-12.99; p=0.0235), while the dark shade of the skin (SMI>75 percentile) with rs16891982 (SLC45A2) (allelic OR =14.37; 95% Cl: 1.78-115.88; p=0.0123). The probability of dark hair (brown and dark brown) in childhood was increased by T rs12913832 allele (HERC2) (OR=3.63); 95% Cl: 2.25-5.85; p < 0.0001) and dependent on it - rs1800401 (OCA2) (OR=6.31; 95% Cl: 1.74-22.91; p=0.0051). Other SNPs were not significantly associated with skin and hair color but improved prediction of these features. Conclusions: From the five gene polymorphisms analysed in Polish children the strongest correlation with hair color has the rs12913832 (HERC2) and with skin color - rs16891982 (SLC45A2). Therefore, the above-mentioned polymorphisms may be used as components of potential models, used to predict pigmentation features in European origin children in prepubertal age. To improve predictive value of the potential scoring model for hair color, the following should be additionally included: rs1800401 (OCA2), rs35264875 (TPCN2) and rs1805007 (MC1R), while for skin color: rs12913832 (HERC2) and rs1805007 (MC1R).