Modeling TEWL-desorption curves: a new practical approach for the quantitative in vivo assessment of skin barrier.

The objective of the present study was to test the discriminative capacity of the mathematical modeling of the transepidermal water loss (TEWL) curves that result from a plastic occlusion stress test (POST) to variations in the skin barrier--insults inflicted to the skin or differences in two distinct anatomical regions. This study was exclusively performed in the arm. On the first part of the work, three different insults to the skin barrier were assessed: tape stripping, lipid extraction with ether : acetone, and skin-surface biopsy. Anatomical differences were studied in the mid-forearm and in the wrist. All sites were submitted to a POST, after which the desorption curves were recorded. The mathematical model was adjusted to the TEWL data points. Results indicate differences in the parameters obtained in the control and treated sites, which suggests differences in the water dynamics after the damage was inflicted and shows that the method is valid for the objectives proposed. There were also significant differences in the parameters obtained in the wrist and in the volar forearm, which indicates that the method is also sensitive to variations in skin histology and anatomy.