Women who use chemical hair straightening products have a better risk of developing uterine cancer than those who do not, consistent with a new study from the National Institutes of Health (NIH).

Researchers found that other hair care products, including dyes, bleaches, brighteners, or perms, weren't associated with uterine cancer.

Respondents to the study included 33,497 U.S. women between the ages of 35 and 74. They participated in a study led by the National Institute of Environmental Health Sciences (NIEHS) of the National Institutes of Health to determine risk factors for breast cancer and other health problems.

The women were followed for nearly 11 years, during which era 378 cases of uterine cancer were diagnosed.

The researchers found that ladies who regularly used hair-straightening products (defined as using them more than four times in the past year) were more than twice as likely to develop uterine cancer as women who did not use them.

"We estimated that 1.64 percent of girls who had never used hair straighteners before age 70 would develop uterine cancer; however, women who used hair straighteners regularly had a 4.05 percent risk of developing uterine cancer.

Alexandra White, the lead author of the study and head of the NIEHS Environmental and Cancer Epidemiology Group, said, "This doubling rate is concerning." it's noteworthy in the context of uterine cancer being a relatively rare form of cancer.

Uterine cancer accounts for about 3 percent of all new cancer cases but is the most common cancer of the female reproductive system. it's expected that there will be 65,950 new cases in 2022. Studies have shown that the incidence of uterine cancer has been rising within the United States, especially among black women.

The researchers didn't collect information on the brands or ingredients of hair care products used by the women. However, they noted in their paper that several chemicals found in hair straightening products, like parabens, BPA, metals, and formaldehyde, may increase the danger of developing uterine cancer.

Chemical exposure from hair products, especially straighteners, could also be of greater concern than from other personal care products because the burns and damage caused by straighteners can exacerbate scalp absorption.

"To our knowledge, this is often the first epidemiological study to examine the relationship between hair straightener use and uterine cancer," White said, "and more research is required to determine whether hair care products contribute to health disparities in women developing uterine cancer, also as to identify specific chemicals that may increase a woman's risk of developing cancer."

The research team also previously found that permanent hair dyes and straighteners may increase the danger of breast and ovarian cancer.