Photo by Arthur Weidmann, Extension siège L'Oréal, licensed under CC BY-SA 2.0. Source: Wikimedia Commons.
A federal judge has cleared the way for key scientific testimony linking chemical hair relaxers to uterine and ovarian cancer, delivering an important ruling for thousands of women suing manufacturers of popular hair-straightening products.
U.S. District Judge Mary M. Rowland issued the decision October 22 in the Northern District of Illinois, where more than 12,700 hair relaxer lawsuits have been consolidated into multidistrict litigation (MDL).
The lawsuits allege that chemical hair relaxers, including products marketed by L'Oréal and other manufacturers, increased users' risks of developing reproductive cancers.
The ruling allows an epidemiologist to testify that chemical hair relaxers are capable of causing uterine and ovarian cancer, rejecting manufacturers' arguments that her scientific analysis was unreliable.
Judge Rejects Challenges to Cancer Expert
At the center of the dispute was Dr. Cote, an epidemiologist who analyzed research examining cancer risks among women who used chemical hair relaxers.
Her conclusions drew on major population studies, including the National Institutes of Health's Sister Study and the Black Women's Health Study.
Those studies identified associations between hair-straightening product use and increased risks of certain reproductive cancers.
The manufacturers challenged the expert's analysis, arguing that she had not adequately established which chemicals caused the cancers or the exposure levels necessary to produce them.
Judge Rowland disagreed that such specificity was required for the expert's testimony to be admitted.
The court concluded that experts may evaluate the potential cancer risks associated with mixtures of chemicals in finished hair relaxer products, rather than having to identify a single cancer-causing ingredient.
Chemical relaxers often contain multiple ingredients whose combined effects may differ from those of individual chemicals.
The judge found Dr. Cote's methodology sufficiently reliable to allow her testimony.
Court Limits Second Expert's Opinions
The ruling was not an across-the-board victory for the plaintiffs.
Judge Rowland also considered testimony from Mr. Atwood, a toxicologist with extensive experience evaluating potentially carcinogenic substances.
Atwood proposed that chemicals in hair relaxers could contribute to cancer through hormonal disruption and absorption through the scalp.
The judge allowed portions of that analysis, finding that his opinions concerning biological mechanisms could help explain how exposure might contribute to cancer development.
However, the court barred Atwood from independently concluding that hair relaxers cause uterine or ovarian cancer.
His proposed testimony concerning inhaled chemicals and certain other mechanisms was also restricted because the judge found insufficient scientific support for those conclusions.
Nearly 13,000 Hair Relaxer Lawsuits Pending
The decision comes as federal hair relaxer litigation continues to expand.
According to the Judicial Panel on Multidistrict Litigation, 12,743 cases were pending in MDL No. 3060 as of November 2, 2026.
Women across the country have filed lawsuits alleging that prolonged use of chemical hair relaxers contributed to diagnoses of uterine cancer, ovarian cancer and other reproductive health conditions.
The litigation has drawn particular attention to product marketing and exposure patterns among Black women, who have historically used chemical hair relaxers at disproportionately high rates.
Research published in the Journal of the National Cancer Institute in 2022 found that frequent use of hair-straightening products was associated with an increased risk of uterine cancer.
The researchers estimated that approximately 1.64% of women who never used hair straighteners would develop uterine cancer by age 70, compared with 4.05% of frequent users.
Those findings helped bring national attention to the potential health risks of chemical hair-straightening products.
However, an observed association in a population study does not, by itself, establish that a particular product caused an individual's cancer.
What's Next for the Hair Relaxer Litigation?
Judge Rowland's ruling addresses two of the ten general-causation experts challenged by the manufacturers. Additional decisions concerning the remaining experts are expected.
The litigation is also moving toward its first bellwether trials, which will allow selected cases to be heard before juries and may help shape future settlement discussions.
The first bellwether trial is currently scheduled for September 2027.
The October ruling does not establish that any particular hair relaxer caused a plaintiff's cancer. Instead, it allows important scientific evidence to be considered as the litigation advances.
For thousands of women pursuing claims, that represents a significant step toward having their cases heard.
The litigation is In re Hair Relaxer Marketing, Sales Practices, and Products Liability Litigation, MDL No. 3060, in the U.S. District Court for the Northern District of Illinois.
References:
U.S. District Court for the Northern District of Illinois. In re Hair Relaxer Marketing, Sales Practices, and Products Liability Litigation. Case No. 1:23-cv-00818, Document 2079. Memorandum Opinion and Order. October 22, 2026.
U.S. Judicial Panel on Multidistrict Litigation. MDL Statistics Report: Distribution of Pending MDL Dockets by Actions Pending. November 2, 2026.
Chang, C.J., et al. Use of Straighteners and Other Hair Products and Incident Uterine Cancer. Journal of the National Cancer Institute. 2022.
National Institutes of Health. Hair Straightening Chemicals Associated With Higher Uterine Cancer Risk. October 17, 2022.