Physico-Chemical Factors Influencing Epidermal Damage by Surface Active Agents

Summary.— The responses of mouse skin to single (10%) and repeated (1% or 2·5%) applications of sodium lauryl sulphate (SLS), cetrimide and Tween‐80 were examined visually and histologically after various periods of exposure. Whereas no damage was caused by Tween‐80 when given as single applications or daily for 9 days, SLS and cetrimide both produced damage. After single applications the changes consisted of epidermal cell degeneration, focal necrosis and dermal inflammatory cell infiltration. After repeated treatment acanthosis and hyperkeratosis were identified, and nuclear debris was present in the keratin layer. Cetrimide‐treated skins were more severely damaged than those treated with SLS. In general, histological changes preceded visual changes by 1 to 2 days. Irritancy due to these surfactants was related to theri physico‐chemical properties. Since Tween‐80 at the concentrations used was highly surface active and lipophilic, these properties were not considered of importance in explaining the damage due to SLS or centrimide. Both of these agents react well with protein such as keratin whereas Tween‐80 does not. Thus it would seem that this property is of primary importance in the production of damage.