Skin Type, but Neither Race nor Gender, Influence Epidermal Permeability Barrier Function

Abstract

Previous studies that compared transepidermal water loss in subjects of different race and sex showed minimal differences in basal permeability barrier function. These studies often did not assess the ability of the stratum corneum to withstand or recover from insults to the epidermal permeability barrier. We compared epidermal permeability barrier function in the following human subjects (age range, 22 to 38 years): white (n = 8) vs Asian (n = 6); male (n = 7) vs female (n = 7); and skin type II/III (n = 14) vs skin type V/VI (n = 7) (scale, I to VI). Basal transepidermal water loss was measured by evaporimetry (three sites) on the volar aspect of the forearm. Barrier integrity then was assessed by determining the number of tape strippings required to reach a transepidermal water loss greater than or equal to 20 g/m2 per hour. The rates of barrier recovery then were compared at 6, 24, and 48 hours and 1 week after abrogation. Neither the number of tape strippings required to perturb the barrier nor the rates of barrier recovery were significantly different in white vs Asian subjects or in female vs male subjects. However, patients with skin types II/III required only 29.6 +/- 2.4 tape strippings to perturb the barrier, while the skin type V/VI group required 66.7 +/- 6.9 tape strippings. Furthermore, while barrier function in skin type II/III recovered by approximately 20% by 6 hours and 55% by 48 hours, barrier function in skin type V/VI, independent of race, recovered more quickly, 43% and 72% at 6 and 48 hours, respectively. Finally, neither the differences in barrier integrity nor in rates of recovery could be attributed to variations in cohesiveness, since stripping appears to remove the same weight of stratum corneum in both groups. Darkly pigmented skin displays both a more resistant barrier and one that recovers more quickly after perturbation by tape stripping than does the skin of individuals with lighter pigmentation. These findings have potential implications for transdermal delivery of topical or systemic therapeutic agents, the ability of individuals with different skin types to withstand environmental or occupational insults, and the influence of acquired hyperpigmentation or pigment loss to influence permeability.