Monitoring the water-holding capacity in visually non-irritated skin by plastic occlusion stress test (POST).

Skin-surface water loss (SSWL) and transepidermal water loss (TEWL) were studied after a plastic occlusion stress test (POST) in visually non-damaged skin treated with 7% sodium lauryl sulphate for 3 days (open application). After removal of the 24-h plastic occlusion, SSWL and TEWL were recorded continuously for 25 min. SSWL decay curves show significant differences between control and treated areas. The total amount of water trapped within the stratum corneum and released after 1 min is significantly reduced (P less than 0.01) in the treated site. Higher TEWL (P less than 0.02) in visually non-irritated skin is noticeable in the terminal part of the curve reflecting the damage of the water barrier in irritated skin. The data suggest that clinically normal skin exposed to subliminal irritant stimuli is less capable of storing water within the stratum corneum resulting in decreased hydration. The POST appears to be a simple and reliable tool to investigate non-visible but biologically relevant changes in stratum corneum function.