Hair product use and the risk of breast cancer in young women

Objectives: The reported mutagenic and carcinogenic effects of some chemica ls present in hair dyes have raised concern that hair dye use could increas e breast cancer risk. This case-control study evaluated how detailed aspect s of hair coloring and hair spray application by reproductive-age women may affect breast cancer risk. Methods: Cases were white female residents of three counties of western Was hington state 45 years of age or less, who were diagnosed with breast cance r between 1983 and 1990 (n = 844). A sample of similarly aged women residin g in the same counties served as controls (n = 960). Information on hair co loring and hair spray use, as well as other exposures, was ascertained duri ng in-person interviews. Results: Breast cancer cases were slightly more likely than controls to rep ort ever having used some type of hair coloring application, including use of rinses, semi-permanent or permanent dyes, as well as bleaching then dyei ng or frosting their hair (relative risk [RR] = 1.3, 95% CI = 1.0-1.6, adju sted for age, fullterm pregnancies, family history of breast cancer, and we ight). In subgroup analyses, women with exclusive use of just one of these methods of hair coloring application had no elevation in risk (similarly ad justed RR = 1.1, 95% CI = 0.9-1.3), whereas women who used two or more of t hese methods did have an elevated risk (RR = 1.9, 95% CI = 1.4-2.5). Hair s pray use was not related to the risk of breast cancer (ever versus never us ers: RR = 1.0, 95% CI = 0.8-1.3). Conclusion: The lack of an association between exclusive use of a single ty pe of hair coloring application and breast cancer risk argues that hair col oring application does not influence breast cancer risk among reproductive- age women. Thus, the results of the present study, as well as negative ones from most (but not all) prior studies, are most consistent with the conclu sion that neither hair coloring application nor hair spray application infl uences breast cancer risk.