Transepidermal water loss for probing full-thickness skin barrier function: correlation with tritiated water flux, sensitivity to punctures and diverse surfactant exposures.

Skin barrier function is a key parameter to consider when performing in vitro percutaneous absorption studies. Whilst tritiated water flux measurements were often used to assess skin integrity, recent decades have witnessed the emergence of the more rapid and user-friendly transepidermal water loss (TEWL) approach. Yet to date, the nature of the correlation between TEWL and skin barrier function in vitro has still not been comprehensively established. In this study, a novel TEWL device, operating on a cold-induced vapour sink principle, was used to probe the barrier function of full-thickness porcine skin. The method was sufficiently sensitive to show the influence of punctures on barrier function although the observed non-linear pattern suggested tissue swelling processes and/or capillary action could be occurring. The results of various surfactant application experiments strongly suggested that TEWL was indeed largely predictive of skin sample integrity. A key finding was that basal TEWL was linearly correlated with basal tritiated water flux (r(2)=0.80, n=63). Thus, a dedicated TEWL method can be used as a good alternative to water flux measurements for assessing full-thickness skin barrier function.