A new study from the National Institutes of Health finds that women who use permanent hair dye and chemical hair straighteners are at a higher risk of developing breast cancer — and the risk is particularly high for black women.
The study, published on Dec. 4 in the International Journal of Cancer, looked at hair product use over a 12-month period in more than 46,000 women ages 35-74 — all of whom have a sister diagnosed with breast cancer. The researchers found that permanent hair dye use in black women was associated with a 45 percent higher risk of breast cancer, while white women had a 7 percent higher risk, according to the study.
Using these hair dyes more frequently upped that risk: Black women using permanent hair dye every five to eight weeks or more was associated with a 60 percent higher risk of breast cancer, compared to an 8 percent increased risk for white women.
Chemical hair straighteners were also associated with a greater risk of breast cancer. Women who used the treatment every five to eight weeks or more were about 30 percent more likely to develop breast cancer; the risk was similar in both black and white women.
It’s not entirely clear why breast cancer risk is especially elevated in black women using permanent hair dye. In general, black women have higher rates of the disease than white women before age 40, and are more likely to die from breast cancer at every age, according to the American Cancer Society.