Clinical Question: Does regular personal use of hair dye increase the risk of cancer?

Setting: Various (meta-analysis)

Study Design: Systematic review

Synopsis: Recent media reports have raised concern about the potential risk of hair dyes causing cancer. In this study, the authors systematically searched multiple electronic databases, reference lists, and meeting abstracts for studies in any language reporting data on personal use of hair dye and risk of cancer. Two persons independently performed the search and data extraction.

The authors performed summary analyses on a total of 79 case-control and cohort studies, including 14 studies on breast cancer, 10 studies on bladder cancer, and 40 studies on hematopoietic cancers. No evidence indicated a significant increase in the risk of bladder cancer or breast cancer with regular use of hair dye. There was, however, an increased lifetime risk of hematopoietic cancers (relative risk = 1.15; 95% confidence interval, 1.05 to 1.27) among regular users of hair dye. The risk of developing other cancers (e.g., brain, ovarian, salivary glands) among hair dye users was evaluated in only one or two small studies, making it difficult to report reliable summary statistics. A formal analysis found no evidence for publication bias.

Bottom Line: Regular personal use of hair dye minimally increases only the lifetime risk of hematopoietic cancers. There is no increased risk of cancers in other sites. (Level of Evidence: 2a–)