Skin Irritancy of Surfactants As Assessed by Water Vapor Loss Measurements

A method to assess the irritancy of chemicals on human skin that is based on measurements of skin (water) vapor loss (SVL) is presented. The SVL measurements were performed with the Servo Med Evaporimeter in a group of 27 healthy volunteers. Four surfactants, distilled water, and NaCl 0.9% in distilled water were assayed. For the exposures a chamber technique was used. Sodium lauryl sulfate and cocobetaine most markedly influenced the loss of water through the skin. Polysorbate-60 and sodium laurate had less effect on SVL. The mean difference between the test substances were found statistically significant, except for the mean difference between sodium laurate and polysorbate-60 (p > 0.1) and between polysorbate-60 and distilled water (p > 0.05). The reactions of the tested subjects to the surfactants suggest that each individual has his own pattern of susceptibility to these substances. The mean values of the SVL measurements were compared with the macroscopically perceptible morphologic changes of the exposed test sites. The results of the visual scoring system corresponded with the results of the SVL measurements. The correlation coefficient between the mean values of both methods was found to be high (r = 0.98)