Hair straightening chemicals linked to higher risk of uterine cancer

Dangers might be greater for Black women, who tend to use the products more often

A new study from the National Institutes of Health links chemicals used to straighten hair with an increased risk of developing uterine cancer.

According to the researchers, women who used these products more than four times a year were more than twice as likely to develop the cancer, compared with people who didn’t use chemical hair straighteners.

For their study, the NIH scientists analyzed data from 33,497 women ages 35-74 who were taking part in the Sister Study, which is led by the National Institute of Environmental Health Sciences. Researchers followed the women for nearly 11 years, during which time 378 participants were diagnosed with 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.”

Although the study found no correlation between increased risk and race, scientists said the dangers might be greater for Black women because they use the products more often. For example, in this study, about 60% of the people who said they used chemical straighteners identified as Black women.

“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., an author on the new study and a research fellow in the NIEHS Epidemiology Branch.

This the NIH’s second study linking hair chemicals to cancer in women. In December 2019, the scientists determined permanent hair dye and straighteners might increase the risk of breast and ovarian cancers.

However, White concluded: “To our knowledge this is the first epidemiologic study that examined the relationship between straightener use and uterine cancer. 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.”

Uterine cancer is the most common cancer of the female reproductive system and accounts for about 3% of all new cancer cases. There have been 65,950 estimated new cases this year. The NIH study was published Monday in the Journal of the National Cancer Institute.

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