Physiological skin surface water loss dynamics of human vulvar and forearm skin

In order to estimate the influence of occlusion and sweating on forearm and vulvar skin surface water loss (SSWL), both were measured simultaneously and continuously for 30 min in 8 healthy women. Vulvar SSWL decreased significantly during the measuring period from 24.9 +/- 5.2 gm-2 h-1 (mean +/- standard error of the mean) in the first 5 min, to 13.4 +/- 1.7 gm-2 h-1 in the last 5 min (p less than 0.05), whereas no significant changes were observed in forearm SSWL. The vulvar SSWL decay curve followed a logarithmic equation of the form y = a*tb. Irregular SSWL increases ('bursts') were observed in vulvar (but not in forearm) skin of 7 out of 8 women. These SSWL bursts were considered to be caused by sweating. The study shows possible causes of systematic errors in vulvar irritation studies. Methods for error reduction are discussed.