Evaluation of Primary Skin Irritation of Surfactants with the Cultured Skin Model

Abstract

It is important to assess the safety of clothes that are used in contact with human skin. In this study the level of primary skin irritation against various surfactants applied to clothes was evaluated using a cultured skin model. The irritation of anionic surfactants depended on the number of carbons in the alkyl substituent. When the number of carbons was in the range from 9 to 12, the surfactants showed positive in the irritation at concentrations higher than 0.5 wt%. However, the anionic surfactants with carbon numbers lower than 9 or higher than 12 showed negative even at concentrations as large as 1 wt%. The cell viability of nonionic surfactants containing poly(ethylene oxide) chains was dependent on the number of chains. The surfactants containing few chains or many carbons showed negative in the irritation assay, while those containing a certain number of chains and the carbon numbers around 10 showed highly positive at concentrations higher than 0.1 wt%. The irritation of quaternary ammonium salts, which are cationic surfactants, showed positive even at low concentrations, regardless of the number of carbons in the alkyl group.