Personal hair dye use and cancer: a systematic literature review and evaluation of exposure assessment in studies published since 1992.

Hair dyes are widely used, and permanent hair dye is the most commonly used type of product. Permanent hair dye colors are formed by an oxidative process involving arylamines, giving rise to concerns about the potential adverse health effects of long-term exposure, especially cancer. A 1993 International Agency for Cancer Research (IARC) review concluded that evidence was inadequate to evaluate the carcinogenicity of personal hair dye use. This systematic review synthesizes the results from studies of personal hair dye use and cancer published since 1993, taking into consideration the quality of exposure assessment. Thirty-one English-language articles published in January 1992-February 2005 that investigated the association between personal hair dye use and cancer were identified through the PubMed search engine. Quality of exposure assessment was rated between 1+ (lowest quality: assessed ever use of hair dyes) and 4+ (highest quality: assessed dye type [permanent/nonpermanent], dye color/shade, frequency and duration of use). Because of the heterogeneity of the exposure assessment across the studies, a formal meta-analysis was not conducted. Associations between personal hair dye use and non-Hodgkin's lymphoma, multiple myeloma, acute leukemia, and bladder cancer were observed in at least one well-designed study with detailed exposure assessment (rated 3+ or 4+), but were not consistently observed across studies. Results for bladder cancer studies suggest that subsets of the population may be genetically susceptible to hair dye exposures, but these findings are based on small subgroups in one well-designed case-control study. Replication of these findings is needed to determine whether the reported associations are real or spurious.