Hair Dyes and Straighteners May Increase Cancer Risk

by DailyHealthPost Editorial

hair dye cancer

New research published in the International Journal of Cancer has revealed that permanent hair dyes and chemical hair straighteners may be unsafe for women, particularly of African-American descent (1). 

This isn’t the first research on the subject either – previous studies on animals had already found a link between certain chemicals in hair dyes and hair straighteners and cancer risk.

The “Sister Study” as it’s been called, worked with a total of 46,709 women between the ages of 35 and 74 (2). According to the study, frequent users of hair dyes and straighteners have a higher risk of breast cancer.


What’s also noteworthy according to epidemiologist Alexandra White (3), is the fact that the risk is significantly higher in black women. Alexandra is a study author and investigator with the National Institute of Environmental Health Sciences.

According to the Sister Study, after 7 years of follow-up, white women have a ~7% increased risk for breast cancer if they’ve been using hair dyes or straighteners while black women have a ~45% increase. The risk increases if the dye or straightener has been used frequently.

This is in line with other statistics, which showed that the risk of breast cancer is generally higher for non-Hispanic black women, especially when more aggressive cancer variants are concerned.

What also complicates the research is those hair products include over 5,000 chemicals, many with mutagenic and endocrine-disrupting properties such as aromatic amines. 

Interestingly enough, with hair straighteners, there was no variation in the cancer risk between black and white women – the increase was 30% for both groups. Black women who use hair straighteners more often than white women which may also explain the overall cancer risk in their group.

“For the chemical straighteners one of the big concerns there is formaldehyde, which is a known carcinogen,” says White. She also notes that Brazilian keratin treatments, also called “Brazilian blowout” became popular in the U.S. just before the study began and they do include formaldehyde as well.


The other interpretation

Dr. Otis Brawley, a medical oncologist at Johns Hopkins University (4), comments that the study’s conclusions need to be viewed in the proper context. “This is a very weak signal that these things might be causing cancer in the population,” and adds that the actual risk associated with hair dyes and straighteners is significantly lower than what the study suggests and when compared with other carcinogens such as tobacco or radiation.

According to Dr. Brawley, long-term clinical trials with control placebo groups are necessary to shed more light on the problem. But such a study “would be very difficult if not impossible to do.”

“Sometimes science just cannot give us the answers that we want it to give us,” says Brawley. He also adds that there are a lot of other factors that need to be considered, especially when it comes to comparing different groups of people. 

“It is for certain that obesity, consuming too many calories and lack of exercise is a risk factor for breast cancer, a definite risk factor,” 

Another oncologist, Dr. Doris Browne, who is also a former president of the National Medical Association, encourages women to have more frequent conversations with their doctors about breast cancer.

“I think it’s important for women, particularly African American women, not to panic every time a study comes out,” she says. “But it should raise questions for our primary care providers.”


Browne accents the point that when talking with a medical professional, patients will be able to get a better perspective not just on the risk of hair dyes and hair straighteners but of other social factors such as obesity, smoking, alcohol, environmental contaminants, and others.

According to her, a key lesson from the Sister Study is that “when we are aware of a new association (of breast cancer risk) we need to increase our surveillance”

Another conclusion of the study was that semi-permanent and short-term hair dyes – the kind that gets washed off easily – have no increased risk of breast cancer.