Key takeaways
- In a large U.S. cohort, women who reported using chemical hair straighteners had higher rates of uterine cancer.
- No association was found for hair dyes, bleach, highlights, or perms.
- The study is observational. It does not prove cause and does not identify a specific ingredient.
What the study did
Researchers at the National Institute of Environmental Health Sciences analyzed nearly 34,000 women ages 35 to 74 in the Sister Study. Participants reported hair product use in the prior 12 months. Over an average follow-up of about 10.9 years, 378 uterine cancers were diagnosed.
What it found
Compared with never using straighteners, ever using them was associated with a hazard ratio of 1.80, and frequent use (more than four times in the prior year) with 2.55. The authors estimated that about 1.64% of women who never used straighteners would develop uterine cancer by age 70, versus about 4.05% of frequent users. About 60% of straightener users in the study were Black women, who the authors note tend to use these products more often and begin earlier. They found no association for other hair products.
Limits
Hair product use was self-reported at baseline, the study is observational, and it cannot say which chemicals are responsible. At the time it was described as the first epidemiologic study to examine this specific question, so replication matters.
Who may want to pay attention
People who use chemical straighteners or relaxers frequently may wish to discuss the findings with a clinician and consider how often they use these products.
Sources
- Chang C-J, O'Brien KM, Keil AP, et al. Use of straighteners and other hair products and incident uterine cancer. J Natl Cancer Inst. 2022. doi:10.1093/jnci/djac165 Source
Last reviewed October 2026. Educational information only, not medical advice. Findings from one study or review do not apply identically to every person or product.