Quantitative measurements of water concentration of the stratum corneum in vivo by high-frequency current.

The superficial portion of the stratum corneum (SC), which is always under the influence of various exogenous factors, easily develops firm and brittle skin surface changes, whenever its hydration state is reduced or whenever there is any functionally deficient area of pathological SC that is unable to retain enough water even in the usual ambient conditions. In contrast, the deeper portion of the SC, which is always well hydrated because of its structural closeness to fully water-saturated viable epidermis, does not pose any serious problems as long as the skin is normal. Based on in vivo and in vitro measurements we have established that high-frequency conductance is a non-invasive technique which measures the hydration state of the superficial portion of the SC, the crucial part determining the physical properties of the skin surface.