Women who use at-home permanent hair dyes face no increased risk of most types of cancer and no higher risk of dying from cancer, according to a major study published Sept. 2.
The research in the BMJ (formerly the British Medical Journal) found no significantly higher risk of brain, bladder, blood, lung, kidney and immune system cancers and most breast and skin cancers from using personal hair dye kits, as reported by CNN.
The study analyzed data from 117,200 nurses over 36 years as part of the Nurses’ Health Study, one of the largest ongoing investigations into chronic disease risk factors for women.
“The headline result is that overall there is no difference in the rate of cancer in general in women who have used hair dyes and those that have not,” Paul Pharoah, a professor of cancer epidemiology at the University of Cambridge in the United Kingdom who was not involved in the study, told Science Media Center.
The study comes amid mixed findings on cancer and hair dye. Last year, researchers found a 45% increased risk of breast cancer among Black women and a 7% increased risk among white women in a study group of 46,709 women who’d used hair dyes or straighteners and also had a sister with breast cancer, as reported by MedTruth.
The BMJ study noted that the International Agency for Research on Cancer of the World Health Organization has classified occupational exposure to permanent hair dye as a “probable carcinogen” and that the U.S. Food and Drug Administration continuously monitors data on hair dye safety. Even so, a 2018 IARC document concludes that there is “limited evidence” for increased cancer risk for barbers and hairdressers and “inadequate evidence” for increased cancer risk from personal use of hair dye.
Although the strengths of the BMJ study include its sample size and duration, the participating nurses were predominantly white, with more than 96% of European descent. The authors note that while previous research into associations between permanent hair dye and cancer have suggested variations across racial and ethnic groups, the current study is of limited generalizability. Nurses, they surmise, may also be better at taking precautions when applying hair dye than the general population. Other limitations include lack of information regarding the nurses’ use of hair straighteners, other types of hair dye and cosmetics and exposure to environmental risk factors such as pesticides.
The researchers did, however, find a slightly increased risk of the following cancers:
- Ovarian cancer
- Three types of breast cancer (estrogen receptor negative, progesterone receptor negative, and hormone receptor negative)
- Skin cancer (basal cell carcinoma) in women with naturally light hair
- Hodgkin’s lymphoma in women with naturally dark hair
Cancer scientist Pharoah cautioned that the link between these cancers and hair dye was “very weak” and were “very likely to be chance findings."
The researchers nonetheless called for additional investigation into cancer risk and hair dye.