SKIN TYPE, BUT NEITHER RACE NOR GENDER, INFLUENCE EPIDERMAL PERMEABILITY BARRIER FUNCTION

Background and Design: Previous studies that compared transepidermal w ater loss in subjects of different race and sex showed minimal differe nces in basal permeability barrier function. These studies often did n ot assess the ability of the stratum corneum to withstand or recover f rom insults to the epidermal permeability barrier. We compared epiderm al 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 fema le (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 t hen was assessed by determining the number of tape strippings required to reach a transepidermal water loss greater than or equal to 20 g/m( 2) per hour. The rates of barrier recovery then were compared at 6, 24 , and 48 hours and 1 week after abrogation. Results: Neither the numbe r of tape strippings required to perturb the barrier nor the rates of barrier recovery were significantly different in white vs Asian subjec ts 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 IV 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 v ariations in cohesiveness, since stripping appears to remove the same weight of stratum corneum in both groups. Conclusions: Darkly pigmente d skin displays both a more resistant barrier and one that recovers mo re quickly after perturbation by tape stripping than does the skin of individuals with lighter pigmentation. These findings have potential i mplications for transdermal delivery of topical or systemic therapeuti c agents, the ability of individuals with different skin types to with stand environmental or occupational insults, and the influence of acqu ired hyperpigmentation or pigment loss to influence permeability.