Frequent use of chemical hair straighteners and relaxers is associated with uterine cancer

2022

Challenge

Use of chemical hair products is very common, yet little is known about how use of these products is related to long-term health outcomes. Limited previous studies have suggested that products used to straighten curly hair may be associated with a higher risk of harmful hormone-related health outcomes, such as breast and ovarian cancers and uterine fibroids. These hair products contain a number of chemicals that may act as carcinogens or endocrine disruptors and thus may be important for cancer risk. Straighteners, in particular, have been found to release formaldehyde, a carcinogenic gas, and contain endocrine disruptors such as phthalates, parabens, and metals. However, there have been no studies of whether hair straighteners and relaxers are associated with the risk of uterine cancer.

Advance

IRP researchers led by Stadtman Investigator Alexandra J. White, Ph.D. M.S.P.H., found that women who frequently used hair straighteners or relaxers, defined as more than four times in the previous year, were more than twice as likely to develop uterine cancer compared to those who did not use the products. The scientists estimated that 1.6 percent 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 percent. Other hair products, including dyes and permanents/body waves, were not associated with a higher risk of uterine cancer. The relationship between hair straighteners and uterine cancer risk was similar for white and Black women; however, Black women were much more likely to use hair straighteners and relaxers.

Impact

This was the first epidemiologic evidence of an association between hair straighteners and relaxers and the development of uterine cancer. These findings are particularly relevant for Black women, who were more frequent users of these products. More studies are needed to confirm these findings, especially in racially and ethnically diverse populations given that hair product use varies notably among women of different race and ethnicities. Rates of uterine cancer are rising, especially among Black women, and thus these hair straighteners and relaxers may be a promising target for intervention to reduce rates of uterine cancer.

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