Viscoelastic properties of intact human skin: instrumentation, hydration effects, and the contribution of the stratum corneum.

Past attempts to relate mechanical properties of the stratum corneum to its state of hydration or disease condition have been hampered by the lack of adequate in vivo methodology. With the technique described herein, viscoelastic properties of the skin surface can be measured in vivo or on excised skin in vitro. This method is sensitive enough to detect changes in the properties of the stratum corneum induced by topically applied agents or by mechanical disruption of it. The viscoelastic data suggest that the outermost layers of the stratum corneum may become dry in vivo despite their proximity to the underlying wet tissue, and that the instrument is sensitive enough to measure the changes that occur. It also appears that the in vivo behavior of the stratum corneum is similar to that of isolated stratum corneum membranes which become brittle when they are dried and supple when they are hydrated.