New study links chemicals in hair straighteners to uterine cancer

Women who often use chemical hair straighteners may be twice as likely to develop uterine cancer as those who never touch the treatments, a new study finds.

The article is the first epidemiological evidence to connect use of hair straighteners and uterine cancer, though the authors say more research is needed on the types of chemicals behind the connection. The study was published in the Journal of the National Cancer Institute.

The article, by National Institute of Environmental Health Sciences, or NIEHS, researchers, is the latest to raise concerns about chemicals in popular hair products. Whether used at a salon or at home, these treatments can create a host of health problems.

Many hair products are made with endocrine-disrupting chemicals, which have been associated with breast and ovarian cancer. Previous studies have linked personal care products containing formaldehyde and other endocrine disruptors, like parabens and bisphenol A, to an increase in fertility problems in people who use them.

Formaldehyde, for example, is a known human carcinogen. Short-term exposure is associated with eye, nose and throat irritation, shortness of breath and wheezing. The chemical also is a potent sensitizer and suspected of increasing the risk of asthma.

Formaldehyde and formaldehyde-releasing chemicals put salon workers at greater risk. The Centers for Disease Control and Prevention has warned that “working with formaldehyde may increase your chances of having fertility problems or a miscarriage.”

Despite shifts in the personal care product industry during the Covid-19 pandemic, hair products remained popular. And as more people stayed home, some wanted to replicate the salon experience by purchasing dyes and straighteners to use themselves.

The use of hair straighteners is common among women in the U.S. Many, particularly Black women, feel social pressure to have straight hair. In the NIEHS study, almost 60 percent of the women who reported ever using chemical straighteners were Black, and the new research highlights the health risks they face.

Salon workers are also exposed daily to chemicals in hair products. Aside from the health hazards caused by inhaling formaldehyde fumes, hair straighteners contain harmful chemicals that can be absorbed through the scalp and worsen the burns caused by the straighteners. 

Past studies linked exposures to hair straightening chemicals with an increased risk of breast and ovarian cancer. The new research now shows a link to uterine cancer.

Calling for safer products

Hair straighteners, like all personal care products, may be brought to market without approval for safety by the Food and Drug Administration.

Last year, EWG petitioned the FDA to ban formaldehyde from so-called Brazilian blowout chemicals and other hair straighteners. Salon workers joined our petition.

The action was a response to a decade of FDA silence about an EWG petition 10 years earlier to ban these chemicals. Our 2011 petition followed an EWG study that found top salons offered formaldehyde-laden hair treatments like Brazilian blowouts.

The FDA has known for over a decade about the risks of hair straighteners. Agency scientists recommended banning formaldehyde from these treatments in 2016, but it failed to act.

Despite formaldehyde being a potent allergen, sensitizer and carcinogen, the FDA has not banned it in hair straightening or -smoothing products. Formaldehyde-laced hair straighteners are still sold and commonly used by salons.

To protect yourself when caring for your hair, consult EWG’s Skin Deep® database to find hazard ratings in personal care products, including hair relaxers, and ingredients of concern.

But stronger federal supervision of the cosmetic industry is needed to keep dangerous products off shelves and protect public health.


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