Women who use permanent hair dye and chemical hair straighteners have a higher risk for breast cancer, according to a new study published in the International Journal of Cancer.
Millions of women and men around the world enhance or change their appearance with hair dye and straighteners.
Consumers can choose from hundreds of hair coloring and straightening products that contain combinations of more than 5,000 different chemicals. The types of chemicals can vary by commercial brand and hair color shade.
In the late 1970s, some hair dye chemicals were linked with cancer in laboratory animals, so many manufacturers removed these chemicals from their products.
However, some dyes on the market today contain substances that are in the same chemical class as those removed, according to the National Institute of Environmental Health Sciences (NIH).
NIH’s Sister Study examines 50,000 sisters of women who have had breast cancer to help determine environmental and familial risk factors for breast cancer and other diseases.
Using data obtained from the Sister Study, researchers found that permanent dye use was associated with 45% higher breast cancer risk in black women and a 7% higher risk in white women.
For black women who used permanent dyes every five to eight weeks or more, the risk increased to 60%.
Hair straighteners were associated with an 18% increase in breast cancer risk.