Women want the dye to be present on the hair, but not on the scalp. Among women with other slow genes (the „CYP1A2 slow“ phenotype), exclusive permanent hair dye use was associated with a 2.5-fold increased risk.
Large epidemiological studies show no elevated health risk for women using hair dyes. Now, an equally important part of the study is those women who were not at increased risk despite using the hair dye. It state that women who used permanent hair dye once a month had a 25% higher rate of bladder cancer.
Women who dye their hair might be different from the average woman in many ways. Those women have turned to at home hair dye kits. I heard of women going bald from over-dyeing their hair, or braiding it. The study of 1,300 women claims that those who started dyeing their hair before 1980 were one-third more likely to develop NHL. The researchers did not find any larger risk of cancer in women who started using hair dye later than 1980. The exception was women who used black hair dye for more than 20 years. Another study found that women who dyed their hair one to four times a year had a greater risk to develop ovarian cancer. Women who smoke and use permanent hair dyes have an even higher risk of cancer.
More studies might look at the risk of cancer from exposure to hair dye at work, which the researchers excluded from this analysis. For hematopoietic cancers, studies found a slightly increased risk of cancer in people who had used hair dye. For bladder cancer and breast cancer, the results indicate that there was no effect of hair dye use on cancer risk.
Risk of salivary cancer increased three times in hair dye users and risk of brain and ovarian cancer almost doubled. Personal use of hair dyes and risk of cancer: a meta-analysis. The researchers found no strong evidence of a link between personal hair dye use and an increase in cancer risk. But researchers have not been able to find a clear link between using hair dye and cancer risk, including the risk of breast cancer. Take-home message. This study supports previous research that found no link between hair dye use and increased risk for breast cancer.