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...