Evaluation of surfactant skin damage by TEWL measurement

Surfactants are compounds with hydrophilic and lipophilic characteristics. These molecules can be divided into four classes: anionic, cationic, nonionic and amphoteric. It is known that most surfactants are potentially irritant to skin through unknown mechanisms. One of the mechanisms inducing irritation can be considered to be the emulsifying of lamellar lipids in the intercellular space of the stratum corneum. The integrity of the stratum corneum controls the rate of transepidermal water loss (TEWL) and a damage of barrier functions modifies TEWL. In this work the determination of TEWL was used to detect the lowest surfactant concentrations inducing barrier damage. We compared this concentration with the minimal irritant concentration clinically detectable. For this purpose the following surfactants have been employed: sodium laurylsulphate, benzalkonium chloride, sorbitan monolaurate and coccoamphoglycinate. Our experiment was carried out on the forearms of ten young male patients, using the 24 hour skin chamber test for each surfactant tested. The TEWL was measured by means of an Evaporimeter EP1 (Servomed) on an exposed area and an unexposed area nearby. This method has proven reliable and more sensitive than clinical observation to evaluate surfactant skin damage and the different individual sensitivity.