Ethnic skin types: are there differences in skin structure and function?¹

Abstract

SynopsisPeople of skin of colour comprise the majority of the world's population and Asian subjects comprise more than half of the total population of the earth. Even so, the literature on the characteristics of the subjects with skin of colour is limited. Several groups over the past decades have attempted to decipher the underlying differences in skin structure and function in different ethnic skin types. However, most of these studies have been of small scale and in some studies interindividual differences in skin quality overwhelm any racial differences. There has been a recent call for more studies to address genetic together with phenotypic differences among different racial groups and in this respect several large-scale studies have been conducted recently. The most obvious ethnic skin difference relates to skin colour which is dominated by the presence of melanin. The photoprotection derived from this polymer influences the rate of the skin aging changes between the different racial groups. However, all racial groups are eventually subjected to the photoaging process. Generally Caucasians have an earlier onset and greater skin wrinkling and sagging signs than other skin types and in general increased pigmentary problems are seen in skin of colour although one large study reported that East Asians living in the U.S.A. had the least pigment spots. Induction of a hyperpigmentary response is thought to be through signaling by the protease-activated receptor-2 which together with its activating protease is increased in the epidermis of subjects with skin of colour. Changes in skin biophysical properties with age demonstrate that the more darkly pigmented subjects retaining younger skin properties compared with the more lightly pigmented groups. However, despite having a more compact stratum corneum (SC) there are conflicting reports on barrier function in these subjects. Nevertheless, upon a chemical or mechanical challenge the SC barrier function is reported to be stronger in subjects with darker skin despite having the reported lowest ceramide levels. One has to remember that barrier function relates to the total architecture of the SC and not just its lipid levels. Asian skin is reported to possess a similar basal transepidermal water loss (TEWL) to Caucasian skin and similar ceramide levels but upon mechanical challenge it has the weakest barrier function. Differences in intercellular cohesion are obviously apparent. In contrast reduced SC natural moisturizing factor levels have been reported compared with Caucasian and African American skin. These differences will contribute to differences in desquamation but few data are available. One recent study has shown reduced epidermal Cathepsin L2 levels in darker skin types which if also occurs in the SC could contribute to the known skin ashing problems these subjects experience. In very general terms as the desquamatory enzymes are extruded with the lamellar granules subjects with lowered SC lipid levels are expected to have lowered desquamatory enzyme levels...

A new Monte Carlo program for simulating light transport through Port Wine Stain skin

“…The procedure, involving 11 iterations for each experiment, took an average of 28 hours to perform over the two validation experiments, using a quad-core processer with The predicted melanin volume fractions are consistent with values published elsewhere for Northern European skin types [11]. Although the spread of melanin through the simulated epidermis differed due to the differences in the initial skin models, the final prediction from the two experiments were similar overall ( Table 2).…”

“…The dimensions and chromophore concentrations of the model layers were based upon the work of Meglinski and Matcher [8], whose parameters are in agreement with experimental studies (for example, [9][10][11]). The layer representing the living epidermis in Meglinski and Matcher's work was divided into two layers in the new programme in order to facilitate differences in melanin properties (Table 1).…”

“…The layer representing the living epidermis in Meglinski and Matcher's work was divided into two layers in the new programme in order to facilitate differences in melanin properties (Table 1). Estimations of representative melanosome concentrations and sizes were based upon an analysis of the literature [11][12][13][14][15][16]. [14].…”

Electromagnetic Signatures of Human Skin in the Millimeter Wave Band 80-100 GHZ

“…The mean differences in emissivity values between Asian and European male participants were calculated to be in the range of 0.04 to 0.11. These differences are likely to be due to higher hydration level and thinner skin of Asian male participants [34][35][36].…”

“…The mean values of the differences in emissivity between Asian and European males were calculated to be ∼0.04 for the inner wrist and the outer wrist locations, ∼0.085 for palm of hand, back of hand and volar side locations, and ∼0.11 for the dorsal surface location. These differences are likely to arise due to Asian skin being thinner than that of European skin and hydration levels and the water contents of the Asian skin being higher than that of European skin [34][35][36]. This makes Asian skin more reflective compared to European skin and as a result the mean emissivity of Asian participants is lower than that of European participants at all measurement locations.…”