Effect of occlusive dressings on the stratum corneum water holding capacity.

Occlusion of the skin is used in clinical dermatology to promote wound healing and to increase the transcutaneous penetration of topically applied drugs. These effects are related to the degree of occlusion exerted and depend on the physicochemical nature of the dressing. We have evaluated the effects of four different materials on the skin barrier and the stratum corneum water holding capacity (WHC) using the Plastic Occlusion Stress Test (POST). The following materials were compared: hydrocolloid dressing, polyurethane film, polyethylene film, and a plastic chamber. These devices were applied on the volar forearm for 24 hours in 10 healthy volunteers (mean age 32 +/- 4 years). Upon their removal, the stratum corneum WHC, measured as skin surface water loss (SSWL), was recorded continuously for 25 minutes using an Evaporimeter. SSWL decay curves showed significant differences between the occlusive materials (analysis of variance, p less than 0.01). Higher SSWL values were recorded in sites occluded with the plastic chamber, whereas the polyurethane film resulted in poor occlusive capacity. Hydrocolloid dressing and polyethylene gave similar responses with higher WHC values compared to polyurethane (p less than 0.05). The relevance of these findings to clinical dermatology in terms of wound healing and drug absorption is discussed.