Natural moisturizing factors (NMF) in the stratum corneum (SC). II. Regeneration of NMF over time after soaking.

The detrimental effects of prolonged water exposure on skin are well known. Information on the effects of short-term exposure, e.g., during bathing, showering, and hand washing, on NMF levels is limited. In an attempt to isolate the effects of soaking on the NMF, a time course for skin sample collection was devised in which adhesive tapes were applied 0.5 and four hours after soaking of the treated arm. Significant decreases in NMF levels, quantified by HPLC analysis of serial tape strips, were observed 0.5 hours after soaking, with a replacement of NMF occurring by the four-hour mark. This replacement corresponds to a parallel rebound in skin pH also observed at these times. Stratum corneum hydration values, measured instrumentally as the rate of moisture accumulation (MAT), however, were depressed 0.5 hours post-soaking and remained low four hours later. In addition, significant increases in skin pH were observed during the immediate post-soak period. These findings suggest that short-term exposure to water alone produces significant changes in the stratum corneum.