Sodium lauryl sulphate for irritant patch testing--a dose-response study using bioengineering methods for determination of skin irritation.

The dose-response relationship in patch testing with sodium lauryl sulphate (SLS) was studied. The irritant skin response was quantified by visual scoring as well as by the following noninvasive methods: measurement of transepidermal water loss (TEWL) by an evaporimeter, measurement of skin color by a colorimeter, measurement of superficial blood flow by laser Doppler flowmetry, and measurement of edema in the skin by ultrasound A-scan. Twelve volunteers were patch tested with 0.12, 0.25, 0.50, and 1.00% SLS, and the skin response was evaluated after 24 and 48 h, respectively. We found a statistically significant linear dose-response relationship between dose of SLS and skin response evaluated by measurement of TEWL, skin color, superficial blood flow, and edema. Statistical evaluation by regression analysis proved measurement of TEWL to be the method best suited overall for quantification in relation to patch testing with SLS, whereas colorimetry was found to be the least sensitive of the applied methods. Ultrasound A-scan was found to be a promising method for quantification of the inflammatory response, being consistently more sensitive than measurement of skin color.