A new approach for an estimation of the equilibrium stratum corneum water content

Background/purpose Water content is the most vital parameter governing the overall function of the epidermal stratum corneum (SC). Thus, knowledge of the in vivo absolute water content of the SC is of great interest. Methods We have investigated a non-invasive method for the estimation of in vivo SC water content based on transepidermal water loss measurements combined with desorption studies of SC in vitro, by means of a dynamic vapour sorption setup where relative humidity (RH) and temperature are controlled. Results The SC equilibrium water content of the volar forearm in our study was estimated to be 80 +/- 7 mu g/cm2. The estimate of the water content seems to decrease slightly with increasing ambient RH. Conclusion The estimated water content is a bit lower than what can be expected to be realistic. A calibration against ambient RH is most probably needed if our method is to be applied over a broad range of values of the RH in the ambient air.