COMPARISON OF IRRITANT POTENTIAL OF SHAMPOOS USING CULTURED HUMAN EPIDERMAL-KERATINOCYTES MODEL AND PATCH TEST REACTION MEASURED BY LASER-DOPPLER FLOWMETRY

The keratinocyte culture model has previously been used as an in vitro method for testing skin irritating potential of common skin irritants . However, solubility limits its use for finished products. Shampoo is very soluble in water which should make it an ideal product category for the cell culture model. To determine the skin irritant potential o f several commercial shampoos, we employed cultured human keratinocyte s as an in vitro model. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetr azolium bromide test (MTT) and lactic dehydrogenase release (LDH) test were used to document cell toxicity. 7 volunteers were patch tested a nd their reactions evaluated using laser Doppler flowmetry and compare d with the in vitro data. MTT and LDH have a good negative correlation with each other. Patch test reaction, especially at high concentratio ns, correlates relatively well with the in vitro test, especially with shampoos of strong and weak irritancy. However, the rank order of the shampoos of moderate toxicity was not the same as in the in vitro dat a. This suggests that the cell culture technique cannot directly repla ce in vivo methods, and that data obtained by the cell culture method should be interpreted carefully.