Facial skin pigmentation is not related to stratum corneum cohesion, basal transepidermal water loss, barrier integrity and barrier repair

Abstract

There was no relationship between ITA° values and basal TEWL, SC integrity, SC cohesion and barrier recovery, but ITA° was correlated with skin hydration. Skin surface pH, irrespective of ITA° values, correlated with SC cohesion, indicating a greater intracorneal cohesion at lower pH values. Thus, pigmentation has no effect on SC barrier properties but was related to skin hydration. On comparing the three ethnic groups, Albino African SC was found to be superior to the Caucasian and Black African subjects in terms of SC integrity and barrier recovery but not basal TEWL. The Albino African subjects also have a thicker SC which contributes to their better SC integrity. No differences in skin barrier functionality or skin surface pH were observed for the other two groups. Skin hydration was, however, greatest in the Black African subjects. Our data support the evolutionary hypothesis that pigmentation protects the skin from UV irradiation and thereby the skin barrier but not the skin pigmentation-/pH-driven adaptive skin barrier hypothesis.

A novel continuous colour mapping approach for visualization of facial skin hydration and transepidermal water loss for four ethnic groups

“…Naturally, when considering the overall data differences among the different ethnic groups were observed. Concerning hydration, the Black African was more hydrated compared with Caucasian skin which was consistent with the reports of others but not all . Equally, the Black African and Indian subjects were more hydrated than the Chinese subjects.…”

“…This finding is consistent with the recent report on facial skin barrier properties reported by Voegeli et al . . Again, this general ranking can be consistent as well as inconsistent with the literature (reviewed in ).…”

“…Numerically but not statistically higher values for the cheek vs. post‐auricular testing sites have recently been reported on three ethnic groups by Voegeli et al . . Tagami has studied the location‐related differences in the stratum corneum (SC) properties on five areas of the face showing that TEWL values increase from the cheek < forehead < nose < chin < nasolabial fold whereas skin hydration measured by skin conductance was nose > chin > nasolabial fold > forehead > cheek .…”

The effect of photodamage on the female Caucasian facial stratum corneum corneome using mass spectrometry‐based proteomics

“…However, in dry skin conditions, non‐peripheral corneodesmosomal proteins are not effectively proteolysed which also contributes to the immature CE phenotype and a thicker ‘ stratum compactum’ . Even though the SC is thinner on the face, a ‘ stratum compactum’ phenotype is also apparent indicating the presence of non‐peripheral corneodesmosomes . Consistent with a lack of CE maturation and changes in desquamation, differences in corneodesmosomal markers were observed between the two body sites.…”

“… also observed increased levels of desmoglein 1, plakoglobin and corneodesmosin, whereas surprisingly desmoglein 1 levels were reported to decline in subjects with dandruff. Increased corneodesmosomal markers can be associated with a thickening of the SC but we had already reported a thinning of the SC in the cheek vs the PA sites . As a result, there must be increased levels of desquamatory enzymes on the cheek leading to an accelerated shedding of ‘stratum disjunctum’ while retaining a stratum compactum phenotype.…”