A study published in the Journal of the National Cancer Institute on Monday suggested that hair-straightening products may contain hazardous chemicals linked to a higher risk of uterine cancer — the most common gynecologic cancer in the United States today.

The study focused on 33,947 women aged 35-74 who “self-reported their use of hair products in the prior 12 months, including hair dyes; straighteners, relaxers, or pressing products; and permanents or body waves.”

Of the 33,947 participants, 378 women developed uterine cancer. Women who used chemical hair straighteners were more than twice as likely to develop uterine cancer than those who had not.

Moreover, the likelihood of developing uterine cancer was directly linked to usage: women who used chemical straighteners more frequently were more likely to develop uterine cancer than those who used the product occasionally.

Black women represented 60% of the participants who reported using chemical straighteners, noted Chanda Jackson, a participant in the National Institute of Environmental Health Sciences Earl Stadtman Investigators program and co-author of the study.

“The bottom line is that the exposure burden appears to be higher among Black women,” she said.

Although relaxers are marketed specifically for black women, all women can use these products.

Straight hair was a popular hairstyle for women of all races in the mid-2000s, but in the following decade, more women began opting for other styles or a natural look. From 2012-2017, hair relaxer sales fell a whopping 38%.

More recently, straight hair has become fashionable again as Gen Z attempts to recapture the styles associated with the early aughts. Milan’s 2021 fashion week displayed the same straight styles with nary a hair out of place.

As straightened hair becomes the norm once again, the authors of the study write, “More research is warranted to confirm our novel findings in different populations, particularly in African American and/or Black women because of the high prevalence of straightener use, and to evaluate the potential contribution of hair products to health disparities in uterine cancer. Future efforts are also needed to identify the chemical ingredients.”