Sorption properties of the human stratum corneum.

Water sorption is important for the overall structure and function of keratinized tissues such as the human epidermal stratum corneum (SC). In this study we report on a gravimetric method for studying sorption properties of human SC, both from heel and female breast skin. Changes in mass were measured as the relative humidity was altered in steps under controlled environmental conditions. The possibility of hysteresis is also discussed. Furthermore, we have found that the sorption time constants show triphasic behaviour during absorption, but not during desorption. This behaviour is connected to the 3 different types of water present in the SC. Water also enters the SC much more rapidly compared to its exit at relative humidities <50%. Finally, the amount of time between sample preparation and onset of measurement seems to have an effect on the absorption rate, but less on the total amount of water absorbed.