The NIEHS Environment and Cancer Epidemiology revealed the shocking results of a study about hair relaxers. According to the institute, people who use chemical hair straightening products are at higher risk for uterine cancer. The National Institutes of Health’s researchers discovered that no other hair products were associated with uterine cancer.

The study led by the National Institute of Environmental Health Sciences (NIEHS), part of NIH, included data from 33,497 U.S. women ages 35-74. In trying to identify risk factors for breast cancer and other health conditions, scientists followed participants for almost 11 years. During that time, 378 uterine cancer cases were diagnosed.

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The researchers found that women who used hair straightening products often were more likely to develop uterine cancer. “We estimated that 1.64% of women who never used hair straighteners would go on to develop uterine cancer by the age of 70; but for frequent users, that risk goes up to 4.05%,” said Alexandra White, Ph.D., head of the NIEHS Environment and Cancer Epidemiology group and lead author on the new study. “This doubling rate is concerning. However, it is important to put this information into context - uterine cancer is a relatively rare type of cancer.”

The NIEHS Environment and Cancer Epidemiology informed uterine cancer is the most common cancer of the female reproductive system, with 65,950 estimated new cases in 2022.

In the United States, Black women are more likely to develop the disease as approximately 60% of the participants who reported using straighteners self-identified as Black, according to the study published in the Journal of the National Cancer Institute.

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“Because Black women use hair straightening or relaxer products more frequently and tend to initiate use at earlier ages than other races and ethnicities, these findings may be even more relevant for them,” said Che-Jung Chang, Ph.D.

The findings are consistent with prior studies showing straighteners can increase the risk of hormone-related cancers in women.

There is no information on specific brands or ingredients; however, parabens, bisphenol A, metals, and formaldehyde could be the chemicals increasing the risks.

“To our knowledge, this is the first epidemiologic study that examined the relationship between straightener use and uterine cancer,” said White. “More research is needed to confirm these findings in different populations, to determine if hair products contribute to health disparities in uterine cancer, and to identify the specific chemicals that may be increasing the risk of cancers in women.”