Oct. 20, 2022 – Clarissa Ghazi gets lye relaxers, which contain the chemical sodium hydroxide, applied to her hair two to three times a year.
A recent study that made headlines over a potential link between hair straighteners and uterine cancer is not going to make her stop.
“This study is not enough to cause me to say I'll stay away from this because [the researchers] don’t prove that using relaxers causes cancer,” Ghazi says.
Indeed, primary care doctors are unlikely to address the increased risk of uterine cancer in women who frequently use hair straighteners that the study reported.
Among frequent users of hair straighteners -- meaning those who used them more than four times a year -- the researchers found that women were 2.55 times more likely to be diagnosed with uterine cancer than those who never used these products.
In the recently published paper on this research, the authors say that they found an 80% higher adjusted risk of uterine cancer among women who had ever “straightened,” “relaxed,” or used “hair pressing products” in the 12 months before enrolling in their study.
This finding is “real, but small,” says internist Douglas S. Paauw, MD, professor of medicine at the University of Washington in Seattle.
Paauw is among several primary care doctors interviewed for this story who expressed little concern about the implications of this research for their patients.
“Since we have hundreds of things we are supposed to discuss at our 20-minute clinic visits, this would not make the cut,” Paauw says.
While it’s good to be able to answer questions a patient might ask about this new research, the study does not prove anything, he says.
Alan Nelson, MD, an internist-endocrinologist and former special advisor to the CEO of the American College of Physicians, says while the study is well done, the number of actual cases of uterine cancer found were small.
One of the reasons he would not recommend discussing the study with patients is that the brands of hair products used to straighten hair in the study were not identified.
Alexandra White, PhD, lead author of the study, said participants were simply asked, “In the past 12 months, how frequently have you or someone else straightened or relaxed your hair, or used hair pressing products?”
The terms “straightened,” “relaxed,” and “hair pressing products” were not defined, and “some women may have interpreted the term ‘pressing products’ to mean non-chemical products” such as flat irons, says White, who is also head of the National Institute of Environmental Health Sciences’ Environment and Cancer Epidemiology group, in an email.
Dermatologist Crystal Aguh, MD, associate professor of dermatology at Johns Hopkins School of Medicine, tweeted the following advice in light of the new findings: “The overall risk of uterine cancer is quite low so it's important to remember that. For now, if you want to change your routine, there's no downside to decreasing your frequency of hair straightening to every 12 weeks or more, as that may lessen your risk.”
She also noted that “styles like relaxer, silk pressing and keratin treatments should only be done by a professional, as this will decrease the likelihood of hair damage and scalp irritation.”
“I also encourage women to look for hair products free of parabens and phthalates (which are generically listed as "fragrance") on products to minimize exposure to hormone disrupting chemicals.”
Not Ready to Go Curly
Ghazi says she decided to stop using keratin straighteners years ago after she learned they are made with several added ingredients. That includes the chemical formaldehyde, a known carcinogen, according to the American Cancer Society.
“People have been relaxing their hair for a very long time, and I feel more comfortable using [a relaxer] to straighten my hair than any of the others out there,” Ghazi says.
Janaki Ram, who has had her hair chemically straightened several times, says the findings have not made her worried that straightening will cause her to get uterine cancer specifically, but that they are a reminder that the chemicals in these products could harm her in some other way.
She says the new study findings, her knowledge of the damage straightening causes to hair, and the lengthy amount of time receiving a keratin treatment takes will lead her to reduce the frequency with which she gets her hair straightened.
“Going forward, I will have this done once a year instead of twice a year,” she says.
White, the author of the study, says in an interview that the takeaway for consumers is that women who reported frequent use of hair straighteners/relaxers and pressing products were over twice as likely to go on to develop uterine cancer compared to women who reported no use of these products in the previous year.
“However, uterine cancer is relatively rare, so these increases in risks are small,” she says. “Less frequent use of these products was not as strongly associated with risk, suggesting that decreasing use may be an option to reduce harmful exposure. Black women were the most frequent users of these products and therefore these findings are more relevant for Black women.”
“We estimated that 1.64% of women who never used hair straighteners would go on to develop uterine cancer by the age of 70; but for frequent users, that risk goes up to 4.05%,” White says in a statement.
“One of the original aims of the study was to better understand the environmental and genetic causes of breast cancer, but we are also interested in studying ovarian cancer, uterine cancer, and many other cancers and chronic diseases,” White says in an interview.