Days after a National Institutes of Health (NIH) study found that women who used chemical hair-straightening products were at higher risk for uterine cancer, a Missouri woman filed the first hair-straightening lawsuit against L’Oreal, alleging that the French company’s hair-straightening products caused her to develop uterine cancer, Reuters reported

The lawsuit, filed Oct. 24 in a federal court in Chicago, comes one week after a research arm of the NIH, the U.S. National Institute of Environmental Health Safety (NIEHS), released data from the so-called Sister Study, which included 33,497 U.S. women ages 35-74 who were followed for over a decade. The study was conducted to identify risk factors for breast cancer and other health conditions and recorded 378 cases of uterine cancer. 

“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,” an NIH summary of the study reported. 

Plaintiff Jennifer Mitchell, who was diagnosed with uterine cancer in 2018, claims she used L'Oreal's hair-straightening products for nearly two decades starting when she was approximately 10 years old. 

Mitchell is seeking unspecified monetary damages and wants L’Oreal to pay for medical monitoring. Mitchell’s attorney told Reuters that other clients have approached her law firm with similar claims against L’Oreal, making it likely that a class action will be filed. 

Rates of uterine cancer are rising, particularly among African-American women, the study indicated. African-American women are more likely to use hair-straightening products. Approximately 60% of the participants who reported using straighteners self-identified as Black women, according to data from the Sister Study, which was published in the Journal of the National Cancer Institute.

“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.

Mitchell, an African-American woman, is accusing L'Oreal of intentionally marketing its hair-straightening products to African-American women and girls. Her lawsuit also claims that L’Oreal has known since at least 2015 that the chemicals in its hair-straightening products could be dangerous and failed to warn consumers about the risks. 

Previous studies have demonstrated that hair-straightening chemicals may increase the risk of hormone-related cancers in women.

The L’Oreal company was not specifically mentioned in the study, nor were other brands or specific ingredients. Several chemicals, including parabens, bisphenol A (BPA), formaldehyde and certain metals may contribute to uterine cancer. Hair-straightening chemicals are particularly concerning because they can be easily absorbed through the scalp.