Does hair dye cause bladder cancer?
There have been several reports of women with long term exposure to hair dyes being at a high risk for bladder cancer. The data certainly isn't clear on that, and there are just as many reports suggesting that there is an association, as those that there aren't. The largest piece of evidence is a Meta analysis which was published in JAMA two years ago. The conclusion of that article was that there is not enough evidence to support the association between hair dyes and the subsequent development of bladder cancer. In the original reports, women who dyed their hair on an average of once a month for five years, had two tenths of a percent higher risk of developing bladder cancer. That figure went to four tenths of a percent over 15 years. When you look at the actual numbers, although the risk seems to be high, the numbers themselves are low. The risk was higher in women who used darker shades (the dark browns, deep blacks and reds) than in the women who used the lighter hair tinting. However, there is no conclusive evidence right now to suggest there is a cause or relationship.
