Chemically straightening and relaxing hair has been commonplace for women – especially Black women – for decades, but a new study published by the National Institutes of Health indicates that there could be a link between chemically straightening hair and uterine cancer.

The 11-year-long study, which was carried out in the US, surveyed nearly 34,000 women between the ages of 35 and 74 who came from diverse racial and ethnic backgrounds. It showed that the women who used chemical straightening products frequently (more than four times in the previous year) were more than two times as likely to develop uterine cancer by age 70 than those who did not. Although Black women made up a minority of the study participants (just 7.4%), they were the demographic that was most largely affected – with 60% of that group reporting to use hair straightening products.

Uterine cancer (also known as womb or endometrial cancer) is the fourth most common cancer in women in the UK and the most common of the five gynaecological cancers, with around 9,700 new cases every year. The researchers found no associations with uterine cancer for other hair products that the women reported using, including hair dyes, bleach, highlights or perms.

“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 percent,” said Alexandra White, PhD, head of the National Institute of Environmental Health Sciences environment and cancer epidemiology group and lead author on the 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.”

A new study has linked chemically straightening hair with uterine cancer: here’s what you need to know