Takkouche B, Etminan M, Montes-Martinez A: Personal use of hair dyes and risk of cancer: a meta-analysis. JAMA 2005;293(20):2516-25.
Does use of hair dye increase cancer risks? About one-third of women in North American and Europe and 10% of men 40 years of age or older use some type of hair dye. The authors reviewed cohort and case-control studies that had been conducted during the past 2 decades and identified 79 studies from which they extracted data for a meta-analysis. The relative risks for ever users of hair dyes was 1.06 (95% CI, 0.95 to 1.18) for breast cancer, 1.01 (95% CI 0.89 to 1.14) for bladder cancer, and 1.15 (95% CI 1.05 to 1.27) for hematopoietic cancers. No effect was observed for users of permanent dyes or for extensive use. There were too few studies to make meaningful assessment of risk for brain or ovarian cancer. Based on these studies, there is no strong evidence of increased cancer risk among users of personal hair dye, although the authors did report a possible borderline association for hematopoietic cancer.