Hair-straightening products may significantly increase the risk of developing uterine cancer among those who use them frequently, a large new study suggests.
The government-run study, led by the US National Institute of Environmental Health Safety (NIEHS), also found that Black women were likely to be more affected because they use hair straighteners more frequently.
The researchers tracked 33,947 racially diverse women, ages 35 to 74, for an average of nearly 11 years. During that time, 378 women developed uterine cancer.
After accounting for participants’ other risk factors, the odds of developing uterine cancer were more than two and a half times higher for women who had used straightening products more than four times in the previous year.
“We estimated that 1.64 per cent 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 per cent,” study leader Alexandra White, of NIEHS, said in a statement.
“However, it is important to put this information into context. Uterine cancer is a relatively rare type of cancer,” she added.
Still, uterine cancer is the most common gynecologic cancer in the United States, according to the US Centers for Disease Control and Prevention (CDC), with rates rising, particularly among Black women.
Black women more exposed
The link between straightener use and uterine cancer did not differ by race in the study, which was published on Monday in the Journal of the National Cancer Institute.
But “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,” Che-Jung Chang of NIEHS said in a statement.
Approximately 60 per cent of the study’s participants who reported using straighteners in the previous year were self-identified Black women.
Endocrine disruptors in hair products
Earlier studies have shown that hair straighteners contain so-called endocrine-disrupting chemicals. The products have previously been associated with higher risks of breast and ovarian cancer.
“These findings are the first epidemiologic evidence of association between use of straightening products and uterine cancer,” White and colleagues wrote in the study.
“More research is warranted to … identify specific chemicals driving this observed association”.
The researchers did not collect information on the brands or ingredients in the hair products that were used. However, they noted that several chemicals that have been found in straighteners (such as parabens, bisphenol A, metals, and formaldehyde) could be contributing to the higher uterine cancer risk observed.
The same team previously found that permanent hair dyes and straighteners may increase the risk of breast and ovarian cancer.