EVALUATION OF SKIN DAMAGE OF CYCLIC MONOTERPENES, PERCUTANEOUS-ABSORPTION ENHANCERS, BY USING CULTURED HUMAN SKIN CELLS

The cytotoxicity of monoterpenes, percutaneous absorption enhancers, t o cultured human skin cells was investigated in order to quantitativel y estimate their skin damage. A neutral red bioassay with epidermal ke ratinocytes and a contraction test of collagen gel in which dermal fib roblasts were cultured were employed for evaluating the cytotoxicity o f terpenes. In the neutral red bioassay, keratinocyte proliferation wa s inhibited on the addition of terpenes, and cell survival remarkably decreased with an increase in the concentration of terpenes fed into t he culture well. When the fibroblasts were cultured in a collagen gel matrix, the lattice of collagen contracted as the cells grew. Therefor e, the application of cytotoxic agents brings about an inhibition of c ollagen gel contraction induced by the fibroblasts. Strong inhibition was observed in the cases of hydrocarbons in terpenes, and the inhibit ion was dependent on the concentration of these compounds added in the culture medium. The cytotoxicity of terpenes was compared with the sk in damage evoked by the application of terpenes in rats in vivo. As a result, it was considered that the skin irritation caused by terpenes was predictable to a certain extent by means of the cytotoxic study of cultured human skin cells.