Diffusion of water vapor through small areas of human skin in normal environment

Abstract

Four small skin areas of the forearm were exposed concurrently to four small bottles at skin temperature. The bottles contained certain wet salts which condition the local vapor pressure. The vapor transfer between skin and bottles resulted in a measurable weight change of the bottles. One thousand tests of 250 people were made in a comfortable room. Below a critical humidity, vapor left the skin; above this "neutral relative humidity" (NRH) the skin gained vapor. A small portion of this skin intake is used to moisten the horny layer. Correcting for this, the average of all tests in NRH = 86%. Frequency curves show two significant maxima besides that around 86%, viz. one around a NRH of 60-70%, generally concurrent with edema, and one above 90% NRH, usually observed on sweating skin. Length of exposure (30 min.-8 hr.), season and skin temperature (excluding sweating) have no recognizable influence on NRH.