Permanent hair dyes and straighteners may increase breast cancer risk

Using permanent hair dye and/or hair straightening products may increase one's risk of developing breast cancer, a new study claims. The risk was found to particularly impact black women based on data from more than 46,700 women who participated in the Sister Study. All of the women were likewise at genetic risk of developing breast cancer, which is itself a risk factor.

The study comes from the National Institute of Health, which reports that it used data with an average follow-up period of more than eight years to assess the potential link between permanent hair chemicals and dyes and the development of breast cancer. Such a link was found, with the study revealing that black women faced a 45-percent greater increase in cancer risk from the use of these products; white women had a 7-percent higher risk.

Breast cancer is particularly common in the United States; it is a notoriously deadly form of cancer that has many risk factors, including a genetic component. For this reason, the researchers only included data on women who had a sister diagnosed with breast cancer, though the participants themselves did not have cancer at the start of their inclusion in the study. A sibling with breast cancer indicated a genetic risk factor for the study participants.

The study notes that permanent hair dye products, which are very commonly used by women in the United States, contain more than 5,000 chemicals, some of which are known to disrupt the endocrine system; others are mutagenic in nature and are known to cause breast tumors in rats. As well, chemical hair straighteners contain risky ingredients like formaldehyde, which is a carcinogen.

Research on this topic is vast but has been, until recently, fairly inconclusive, with some studies showing risk and others showing no risk. The latest study points toward more recent research that has found increased risk of developing both breast cancer and bladder cancer in association with permanent hair dye.

Fewer studies have looked into the cancer risks of chemical hair straighteners, however, which are most commonly used by black women. The use of these products may explain why breast cancer risk was found to be substantially higher in women of African descent versus white women. Questions remain, such as what influence the frequency of use has on risk, as well as whether it's potentially safer to use hair dyes and highlighters that do not contact the skin.