Hair Relaxers Linked to Additional Cancer Risks as Litigation Moves Toward Trial

NIH Study Expands Cancer Concerns

A newly published analysis from the National Institutes of Health’s ongoing Sister Study adds to mounting evidence that chemical hair straighteners may increase cancer risk. Earlier research primarily focused on reproductive cancers such as breast, ovarian and uterine cancer. The latest findings suggest the potential risks may extend further. Researchers reported associations between chemical hair straightener use and higher incidence of pancreatic cancer and thyroid cancer, along with a possible link to non-Hodgkin’s lymphoma. The findings broaden concern about how repeated exposure to certain cosmetic chemicals may affect long-term health.

The Sister Study followed more than 46,000 women between the ages of 35 and 74 who were cancer-free at enrollment but had a family history of breast cancer. Participants provided detailed health and lifestyle information and were tracked for years through medical records and mortality data. Investigators categorized straightener use based on reported frequency within the prior year.

Scientists emphasized the broader public-health implications of the findings. Because hair relaxers are widely used — often beginning in childhood and disproportionately among Black women — even modest increases in cancer risk could affect large populations. Researchers noted that environmental exposures and consumer products may account for a significant portion of lifetime cancer risk, underscoring the importance of evaluating everyday chemical exposures.

Hair straightening products have been shown to contain or release compounds such as formaldehyde and phthalates, chemicals associated with endocrine disruption and carcinogenic mechanisms. While the study does not establish direct causation, it strengthens biological plausibility for claims that chronic exposure may contribute to cancer development. Although the authors cautioned that the research has limitations, they concluded that the results expand the scope of potential adverse health outcomes linked to chemical straighteners and warrant further investigation.

Litigation Growing

Hair relaxer lawsuits have been consolidated into multidistrict litigation (MDL No. 3060) in the Northern District of Illinois before U.S. District Judge Mary M. Rowland, and is one of the largest product-liability proceedings currently in federal court. There are 11,195 pending cases as of February 2026 – filed by women alleging that regular use of chemical relaxers caused uterine, ovarian or endometrial cancers and other injuries.

In January 2026, the court held a “Science Day,” a non-adversarial proceeding designed to educate the judge about the complex medical and scientific issues underlying the litigation. Experts and attorneys presented research addressing plaintiffs’ theories of causation and manufacturers’ defenses, helping the court prepare for upcoming rulings on expert testimony and admissibility of scientific evidence. Such proceedings are common in large MDLs where scientific questions play a main role. Such presentations are not part of the official trial record and are not subject to cross-examination, but they often influence how courts evaluate competing expert opinions later in the case.

Judge Rowland previously ordered the parties to identify 32 representative lawsuits to form a bellwether discovery pool — cases intended to test how juries respond to evidence likely to appear repeatedly across thousands of claims. Under new scheduling orders issued in early 2026, fact discovery for those cases must be completed by March 18. Attorneys will then propose 12 cases for potential trial selection, from which the court will choose several claims to proceed toward the first bellwether trials.

The judge is expected to select initial cases by April, with additional discovery continuing into mid-2026. The first trials, however, are not anticipated to begin until 2027.

Science and Law in Synch

The convergence of expanding scientific research and advancing courtroom proceedings highlights the stakes surrounding hair relaxer safety. New epidemiological evidence suggesting links to additional cancers may shape both regulatory discussions and future legal arguments over causation.

For thousands of women pursuing claims, the upcoming bellwether trials represent a pivotal moment. The outcomes could determine not only potential compensation but also how courts and juries interpret the growing body of research examining whether everyday cosmetic products carried risks that consumers were never warned about.