Does hair dye use really increase the risk of prostate cancer?

Recently, Shu-Yu Tai et al. reported that personal hair dye use increased risk of prostate cancer with a dose-response effect. Although hair dyes were identified as carcinogenic in animals and increased risk of some cancers among hairdressers, the existing epidemiological data did not support that personal hair dye use increased risk of cancers, even for bladder cancer. Given that Tai et al.’s report of a potential hazard of personal hair dye use on risk of prostate cancer was particular, the methodology of the study was scrutinized and some flaws were found including the issue of external validity.