There are nearly 13,000 chemicals found in personal care products sold in the U.S., and only 10% have been tested for safety. Considering that fact, it shouldn’t come as a huge surprise that a recent study linked permanent hair dyes and chemical straighteners — both of which are full of questionable ingredients — to an increased risk of breast cancer.
To conduct the study, published in the International Journal of Cancer, researchers tracked 46,700 American women who were breast-cancer-free, but had sisters who had been diagnosed with the disease. The women, ranging from 35 to 74 years old, answered questions during the enrollment period about their health, demographics and lifestyle, including questions about hair product use. Each participant provided researchers with a updates over a follow-up period of on average, eight years.
More than half of the women reported using permanent hair dyes in the year before the study began, and around 10% reported using chemical straighteners. Researchers found that these women had an increased risk of developing breast cancer. The study showed that overall, women who used permanent hair dye were 9% more likely to develop breast cancer, compared to those who did not dye their hair. Researchers also found that black women who used permanent hair dye were 45% more likely to develop breast cancer, compared to those who did not dye their hair. Women who reported using chemical straighteners — 74% of black women and 3% of white women — were 18% more likely to develop breast cancer.
The researchers noted that black women are more likely to develop the subtype of breast cancer that appears most related to hair dye and straighteners, and black women are more likely to die from breast cancer than white women. Alexandra White, an epidemiologist at the National Institute of Environmental Health Sciences, suggested this may be due to the differences in formulations of dyes and straighteners used by black women, compared to those used by white women.
White also noted, “Hair dye contains more than 5,000 different compounds… and formulas are constantly changing. Some compounds have had more evidence to support their possible carcinogenicity than others.”
When it comes to breast cancer, White said some of the most dangerous hair dye ingredients are aromatic amines — colorless chemicals in hair dye that can bind to DNA in breast tissue and potentially damage DNA and lead to cancer.