There is more serious news concerning the chemicals in hair straightening products and increased cancer risk. We have published studies* with similar findings over the past decade and a half. This latest scientific study was funded by the United States Institutes of Health (NIH) and researchers found that women who used chemical hair straightening products were at higher risk for uterine cancer** compared to women who did not report using these products.
The study data included 33,497 U.S. women ages 35-74 participating in the Sister Study, a study led by the National Institute of Environmental Health Sciences (NIEHS), part of NIH, that seeks to identify risk factors for breast cancer and other health conditions. The women were followed for over a decade (almost 11 years) and during that time 378 uterine cancer cases were diagnosed.
The researchers found that women who reported frequent use of hair straightening products, defined as more than four times in the previous year, were more than twice as likely to go on to develop uterine cancer compared to those who did not use the products.
Approximately 60% of the participants who reported using straighteners in the previous year were self-identified Black women, according to the study published in the Journal of the National Cancer Institute. Although, the study did not find that the relationship between straightener use and uterine cancer incidence was different by race, the adverse health effects may be greater for Black women due to higher prevalence of use. The findings are consistent with prior studies showing straighteners can increase the risk of hormone-related cancers in women.
Other findings of note
Several chemicals that have been found in straighteners (such as parabens, bisphenol-A, metals, and formaldehyde) could be contributing to the increased uterine cancer risk observed. Chemical exposure from hair product use, especially straighteners, could be more concerning than other personal care products due to increased absorption through the scalp which may be exacerbated by burns and lesions caused by straighteners.
*Some other scientific studies we have published linking chemicals in hair care products to adverse health outcomes:
**Uterine cancer accounts for about 3% of all new cancer cases but is the most common cancer of the female reproductive system, with 65,950 estimated new cases in 2022. Studies show that incidence rates of uterine cancer have been rising in the United States, particularly among Black women.
Journal reference: Che-Jung Chang, Katie M. O’Brien, Alexander P. Keil, Symielle A. Gaston, Chandra L. Jackson, Dale P. Sandler, Alexandra J. White. Use of Straighteners and Other Hair Products and Incident Uterine Cancer, Journal of the National Cancer Institute, 2022. DOI: https://doi.org/10.1093/jnci/djac165