OBJECTIVE:

We compared, updated, and expanded the analyses of two previous meta-analyses of personal hair dye exposure and bladder cancer, and briefly discussed the biological plausibility of a systemic hazard to human health from exposure to para-phenylenediamine (PPD), a key chemical in hair dyes.

METHODS:

The meta-analysis included 11 case-control studies and one cohort study. We evaluated heterogeneity across studies and conducted sensitivity and influence analyses.

RESULTS:

No association was found between any personal use of hair dye and bladder cancer among women (meta-relative risk [mRR] = 1.01, 95% CI: 0.89-1.14), men (mRR = 0.82, 95% CI: 0.60-1.14), or both sexes combined (mRR = 0.97, 95% CI: 0.87-1.08). No statistically significant mRRs were found among the studies that reported data for permanent hair dye use (mRR = 1.06, 95% CI: 0.89-1.27), duration of any hair dye use (mRR = 1.00, 95% CI: 0.85-1.19), duration of permanent hair dye use (mRR = 1.31 95% CI 0.78-2.19), lifetime applications of any hair dye use (mRR = 1.12 (95% CI: 0.72-1.72) or permanent hair dye use (mRR = 1.59, 95% CI 0.69-3.64), or dark color hair dye use (mRR = 0.94, 95% CI: 0.74-1.19).

CONCLUSION:

The results of this meta-analysis of epidemiologic studies do not indicate a causal association between personal hair dye use and bladder cancer.