Hypothetical scenario for illustration only: Imagine you have used a chemical relaxer since your early teens, as have your mother and aunts. You see a headline saying relaxers cause cancer, and you do not know whether to panic, throw out your products, or dismiss it as another scare story. That uncertainty is reasonable — and it deserves a careful answer.

Why This Matters for Black Women Specifically

Chemical hair relaxers have historically been marketed almost exclusively to Black women. The National Institutes of Health estimates that roughly two-thirds to three-quarters of Black women in the United States have used them at some point. That level of exposure means that even a modest increase in risk, if real, would affect a large number of people. Meanwhile, Black women already face higher rates of uterine cancer mortality than white women, in part because of delayed diagnosis and barriers to care.

What the Research Found

Two large observational studies have reported associations between relaxer use and uterine cancer in Black women.

The first, published in the Journal of the National Cancer Institute in 2022, used data from the NIH Sister Study — a prospective cohort of more than 33,000 women followed since 2003. Researchers found that women who reported using chemical straighteners frequently (more than four times in the prior year) had a higher risk of developing uterine cancer compared with women who never used them. The hazard ratio was approximately 2.5 among frequent users. A hazard ratio of 2.5 means frequent users developed uterine cancer at a rate about 2.5 times that of non-users over the study period — it is not a statement that any individual’s probability of cancer is 2.5 times higher. Uterine cancer remains relatively uncommon; the absolute risk numbers were small.

The second study, published in 2023 from Boston University’s Black Women’s Health Study — the largest prospective cohort of Black women ever assembled, following nearly 45,000 women for up to 22 years — found that postmenopausal Black women who used relaxers more than twice a year or for more than five years had over 50% higher uterine cancer rates than women who never or rarely used them.

Both studies adjusted for known risk factors including BMI, age at menopause, and hormone use. Researchers believe the potential mechanism involves endocrine-disrupting chemicals — including parabens, phthalates, and cyclosiloxanes — detected in some relaxer formulations that may interfere with estrogen signaling.

What the Evidence Does Not Establish

Both studies are observational, which means they identify associations, not causation. It is possible that women who use relaxers more frequently share other characteristics — related to stress, diet, healthcare access, or other chemical exposures — that partly explain the elevated rates. Neither study was designed to isolate relaxers as the cause.

Additionally, the Sister Study enrolled mostly postmenopausal women and overrepresented women with a family history of breast cancer, which may limit how well findings generalize to all Black women. Product formulations have varied widely over decades, and women were asked to recall use going back years, introducing potential recall error.

Practical Steps to Consider

When to Seek Evaluation