THE LYES THAT CAN KILL YOU

Women who used chemical hair straightening products were at higher risk for uterine cancer compared to women who did not report using these products, according to a new study from the National Institutes of Health. The researchers found no associations with uterine cancer for other hair products that the women reported using, including hair dyes, bleach, highlights, or perms.

The study data includes 33,497 U.S. women ages 35-74 participating in the Sister Study, a study led by the National Institute of Environmental Health Sciences (NIEHS), part of NIH, that seeks to identify risk factors for breast cancer and other health conditions. The women were followed for almost 11 years and during that time 378 uterine cancer cases were diagnosed.

The researchers found that women who reported frequent use of hair straightening products, defined as more than four times in the previous year, were more than twice as likely to go on to develop uterine cancer compared to those who did not use the products.

“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.”

Uterine cancer accounts for about 3% of all new cancer cases but is the most common cancer of the female reproductive system, with 65,950 estimated new cases in 2022. Studies show that incidence rates of uterine cancer have been rising in the United States, particularly among Black women.

In 2021, another study found that frequent and long-term use of lye-based hair straightening products, or relaxers, may increase the risk of breast cancer among Black women, compared with more moderate use.

Boston University’s Black Women’s Health Study followed 59,000 self-identified African American women for over 25 years, sending questionnaires every two years on new diagnoses and factors that might influence their health.

The study found that Black women who used hair products containing lye at least seven times a year for 15 or more years had an approximately 30% increased risk of estrogen receptor positive breast cancer compared with more infrequent users.

There is an urgent need to address racial disparities in breast cancer. Black women diagnosed with breast cancer are 40% more likely to die from the disease than white women. While systemic factors such as delays in diagnosis and poorer health care likely contribute to this disparity, they don’t seem to fully explain the survival gap between Black and white women.

Black women are more likely than white women to develop highly aggressive breast cancers that have higher mortality rates, but researchers don’t really know why. However, scientists do know that chemical hair relaxers, more often used by Black women, contain potentially harmful chemicals, including possible carcinogens and chemicals known as endocrine disrupters, which can interfere with hormone function and could raise breast cancer risk. In the Black Women’s Health Study, 95 percent of women reported past or current use of these products.

This study fills a knowledge gap on the potential health effects of a consumer product popular among Black women. Given these findings, women may want to be cautious about the types of personal-care products they choose.

Thanks to 59,000 study participants in the Black Women’s Health Study, our research team continues to investigate risk factors for breast cancer and other diseases in Black women. By understanding what causes disease and learning about ways to lower risk, society can move one step closer toward eliminating health disparities.