But now research warns that the use of straighteners, relaxers, and other hair products is linked to uterine cancer. The study, which was published earlier this week, comes at a time when some Black women who previously wore their hair naturally have either returned to relaxers or are considering doing so. 

“Frequent and especially long-term use of some hair straightening products can affect long-term health. This is particularly important for Black women to know as the natural-to-relaxer movement gains momentum,” says Dr. LaTasha Perkins, a family physician based in Washington, D.C., who was not involved in the study

The hashtag #RelaxersAreBack has 5.3 million views on TikTok to date and features Black women getting relaxers at the salon or doing it themselves at home. To combat new growth, it is common to get a relaxer every six to eight weeks, or roughly six times per year.

According to researchers, hair products may contain hazardous chemicals with “endocrine-disrupting and carcinogenic properties.” Previously studies have demonstrated certain hair products come with a higher risk of breast and ovarian cancer, but this is the first one to show an association with uterine cancer.

The study, referred to as the Sister Study, involved nearly 34,000 participants between the ages of 35 and 74 who did not have breast cancer but had at least one sister diagnosed with the disease. Researchers evaluated their self-reported use of hair products, such as hair dyes, straighteners, relaxers, and body waves within the prior 12 months. 

Most of the participants were white and did not include a sufficient sample of Black participants to determine association with the group even though the authors recognized that adverse effects are more likely with this group given “higher prevalence of use, initiation at younger ages, and more toxic formulations.” 

“The risk of developing uterine cancer for frequent users of relaxers is 4.05% compared to 1.64% for women who’ve never used hair straightening products—a number worth paying attention to,” says Perkins. “Mind you, uterine cancer is generally rare, but is the most common cancer of the female reproductive system according to the study.”

Over an average follow-up of 10.9 years, 378 uterine cancer cases were identified in the study. It is believed that the endocrine-disrupting chemicals found in the hair products could contribute to uterine cancer risk “because of their ability to alter hormonal actions.” Researchers also observed an 80% higher risk of uterine cancer among participants who used hair-straightening products, with the risk more than double for women who used the products more than four times in the previous year.

“Generally speaking, cancer is the abnormal replication of cells that spread to other parts of the body. Hormone-disrupting chemicals like parabens, formaldehyde, and metals, which are commonly found in hair straightening products, have been connected to all sorts of cancer,” explains Perkins. “When we put chemicals like this on our scalps, a highly porous part of our body, those chemicals are absorbed and enter our bloodstream. This can prompt the growth of abnormal cells, and eventually result in a case of uterine cancer, for example. Hormone-disrupting chemicals disrupt the natural course of cell development.”

As the natural-to-relaxer movement grows, Perkins urges caution for those considering a return to relaxers.

“Before you make the decision to return to a relaxer, please educate yourself on what you’re putting on and in your body. Take the time to understand the composition of your preferred relaxer and consider formaldehyde-free or lye-free options, for example,” she says. “Your scalp is a reservoir for absorption, so be mindful of how certain chemicals could affect your health in the long run. And remember, there are ways to get the same look through alternative hair styling methods.”

Some alternatives to relaxers that achieve the same straight hair look are blowouts, silk presses, wigs, and extensions, such as sew-in weaves. “The important thing is to be mindful of potentially toxic chemicals being used to achieve those styles,” warns Perkins.

If you’re unsure about which ingredients may be harmful, Perkins encourages people to call their family physician.

“I want Black women to feel empowered to choose safer options,” says Perkins, who stopped relaxing her hair more than 20 years ago and currently wears her hair in locs. “There wasn’t much research on the health repercussions of relaxers then, but the more I learned about how chemicals absorb into the scalp, the less comfortable I was using relaxers…I want to encourage more Black women to consider alternatives to relaxers, defining what beauty means to them along the way.”