Evaluation of the toxicity and carcinogenicity of hair dyes.

The chronic toxicological and carcinogenic potential following skin painting in mice was evaluated for nine oxidative and three nonoxidative hair dyes. Groups of male and female Swiss mice were treated one time weekly for at least 20 mo with one dose level of each dye. The oxidative dyes were mixed 1:1 with 6% hydrogen peroxide before treatment and the three semipermanent formulations were applied without dilution. Control groups were shaved only and received no applications. Body weights and survival rates did not differ between appropriate male and female treatment and control groups. Absolute and relative liver and kidney weights were equivalent for treatment and control groups. After 7 and 9 mo of treatment, 10 males and 10 females randomly selected from each group were necropsied and tissues taken for histopathologic evaluation. Animals found dead or sacrificed in moribund condition or at termination of the study were necropsied and evaluated histopathologically. Comparison of incidence of tumors and of nontumor pathology among the various treatment and control groups revealed no biologically significant differences. Toxicological and carcinogenic effects were not induced by the hair dye formulations.