- Researchers say women who use permanent hair dye and chemical hair straighteners have a higher risk for breast cancer.
- The risk was significantly higher for black women than for white women.
- However, experts say women shouldn’t give up hair products based on this study alone.
We already know many
There are those you can’t change, such as sex, age, and genetics.
There are some you can change, like sedentary lifestyle and alcohol consumption.
Whether or not you develop breast cancer is likely not due to a single thing but a combination of factors. One of those factors may be exposure to certain chemicals.
Chemical hair dyes and straighteners contain more than 5,000 chemicals, say the authors of a new study published in the International Journal of Cancer.
Researchers at the National Institute of Environmental Health Sciences, part of the National Institutes of Health (NIH), looked at chemical hair dyes and straighteners to see if they’re linked to increased breast cancer risk.
They say their study supports the theory that women who use permanent hair dye and chemical hair straighteners have a higher risk for developing breast cancer than those who don’t.
The rise in risk was lower for women who have their hair done in a salon. Using semipermanent or temporary dye was associated with little to no increase in risk.
Experts say there’s a lot to learn from this study, but they caution that it doesn’t prove cause and effect.
The researchers used data from 46,709 women who enrolled in the Sister Study between 2003 and 2009.
Participants were between the ages of 35 and 74 and came from all 50 states and Puerto Rico. None had a personal history of breast cancer, but all had a sister with a breast cancer diagnosis.
The researchers factored in such variables as socioeconomic status, reproductive history, and menopausal status.
Average length of follow-up was 8.3 years.
Study participants who used hair dye tended to be younger, have fewer years of education, were more likely to be current smokers, and more likely to have used oral contraceptives.
Black women, postmenopausal women, and those who had fewer children were less likely to have used permanent dye.
As a whole, women who regularly used permanent hair dye in the year before enrolling in the study were 9 percent more likely to develop breast cancer than those who didn’t use these products.
For black women, the increase was 45 percent, while it was 7 percent for white women.
According to the researchers, products marketed to black women have higher concentrations of estrogens and endocrine-disrupting compounds.
The use of permanent dyes every 5 to 8 weeks or more was associated with a 60 percent increased risk of breast cancer for black women. The increase in risk was about 8 percent for white women.
Overall, using chemical straighteners in the year before enrollment was associated with an 18 percent increase in risk.
The researchers found that women using hair straighteners every 5 to 8 weeks were about 31 percent more likely to develop breast cancer. The association was about the same for black and white women, but more black women used straighteners.
Study authors wrote that the research highlights “potential differences in associations by ethnicity” and the findings “have the potential for substantial public health impact.”
Dr. William J. Gradishar is a professor of breast oncology, director of the Maggie Daley Center for Women’s Cancer Care, and director of Breast Medical Oncology at Robert H. Lurie Comprehensive Cancer Center at Northwestern University in Illinois.
Gradishar told Healthline that the study’s conclusions were based on a large number of participants. That’s a positive element.
“But as usual with survey data, when asking what patients did or did not do, or what they were exposed to, there’s always a risk of having some error in recall,” he said.
“None of the women got genetic testing, so we don’t know if they were at higher risk. Some probably were, which might explain some of the observations made,” Gradishar said.
Gradishar, who chairs the National Comprehensive Cancer Network (NCCN) Guidelines Panel for Breast Cancer, says it’s difficult to know whether these observations are applicable to the broader population.
“We don’t want to dismiss these results, but one has to be cautious about overinterpreting them,” Gradishar said.
Study authors acknowledged they didn’t evaluate the formulation of the various dyes or straighteners used. Use of hair products throughout the follow-up period wasn’t considered.
“I’m not surprised at a potential connection between hair dye and breast cancer,” she told Healthline. “There are chemicals in dyes that act as estrogen disrupters and other chemicals that are carcinogenic.”
Bernik doesn’t have absolute confidence that hair products are the reason study participants developed breast cancer.
“It was a select group of women. Every participant had a sister with breast cancer, so they already had elevated risk,” she explained.
“Many things we once held to be true about breast cancer risk turned out not to be the case. The bottom line is that more studies should be done to prove it. This one indicates that it may increase breast cancer risk, not that it does,” Bernik said.
Gradishar suggests that women shouldn’t be overly concerned or necessarily stop using hair products based on this study alone.
“We need to be cautious about scaring everybody,” he said.
Bernik advises women to be careful when using permanent hair dyes or straighteners at home. Use gloves and follow package safety warnings.
For those who are worried or fall into high-risk groups, she recommends looking at alternatives, such as using semipermanent dye or going to a salon.
According to the American Cancer Society, the average lifetime risk of developing breast cancer is 13 percent for women in the United States. It’s less common than skin cancers.
The higher risk for black women is something we’ve known for a long time, says Gradishar.
In particular, black women have a greater frequency of triple-negative breast cancer.
“There are a lot of individual things we’ve known for decades that contribute to elevated risk, and perhaps this [dyes and straighteners] will be another. But none exist in isolation,” he said.
Gradishar advises all women to get screening mammograms as recommended.
Bernik says that if you’re concerned about breast cancer risk, a low fat diet and regular exercise go a long way.
“Previously we have found that if you lead a healthy lifestyle, you’re less likely to get cancer. That’s really proven,” she said.