Judge Allows Key Expert Testimony Linking Hair Relaxers to Cancer
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A federal judge has ruled that a key expert for women suing over chemical hair relaxers can testify that the products are capable of causing uterine and ovarian cancer.
U.S. District Judge Mary M. Rowland issued the ruling on Oct. 22 in the federal hair relaxer multidistrict litigation (MDL) in the Northern District of Illinois.
The decision is a significant early win for plaintiffs who have filed hair relaxer lawsuits, but the court has not yet ruled on most of their experts.
What the Hair Relaxer Judge Decided
The judge rejected the manufacturers’ bid to exclude Dr. Cote, an epidemiologist who studies disease patterns in large groups of people.
Dr. Cote concluded that people who frequently use relaxers face higher cancer risks, with reported increases ranging from 20% to about 250%.
The manufacturers argued that the plaintiffs’ experts did not show how much chemical exposure it takes to cause cancer. They also argued that plaintiffs must identify a specific cancer-causing ingredient or exact chemical “recipe,” but the judge disagreed.
“Plaintiffs may use a mixture as the relevant causal exposure, may reason from defined causal classes of chemicals, and do not have to provide specific recipes,” Rowland said.
That means plaintiffs can argue the mix of chemicals in the finished products is what raises cancer risks.
Limits Placed on a Second Expert
A second plaintiffs’ expert, toxicologist Mr. Atwood, received a split ruling. Atwood spent more than 20 years evaluating potential carcinogens for the National Toxicology Program.
He may testify that hormone-disrupting chemicals and side effects in hair relaxers make a cancer link biologically plausible, including through absorption into the skin. However, he cannot give his own opinion that relaxers cause cancer, and he cannot claim that inhaled fumes are an established route of exposure.
The judge also barred him from folding formaldehyde into his theory of how the chemical mixtures could cause cancer. The court found his report did not cite a scientific source for that part of his opinion.
Drs. Cote and Atwood are only two out of the 10 plaintiffs’ expert witnesses that the defendants have objected to. The judge may rule on the objections to the remaining experts.
Judge Rowland stressed that her role was to assess the experts’ methods, not to decide who is right about the science. Manufacturers can still challenge Dr. Cote at trial.
What Happens Next in The Hair Relaxer MDL?
The parties face a Nov. 16 deadline to file summary judgment motions and remaining expert challenges. Replies in support of these motions are due Jan. 6, 2027.
In a separate Oct. 22 docket entry, the judge noted that the parties had picked the final five bellwether cases. Bellwether trials are test cases chosen to represent the broader litigation and help guide settlement talks.
The first bellwether trial against L’Oréal USA is set to begin on September 9, 2027.
As of November 2026, 12,743 hair relaxer lawsuits were pending in the federal MDL, and no global settlement has been announced.
The federal lawsuits are separate from consumer protection cases that Minnesota and Arizona have filed against L’Oréal.
Lawyers are still accepting cases in 2026.
Editor Arsheeya Garg contributed to this article.