Hair Relaxer Lawsuit Timeline: From the Sister Study to 11,877 Pending Federal Cases

2021 and 2022: research changes the public conversation

In June 2021, researchers using the National Institute of Environmental Health Sciences Sister Study published an analysis of 40,559 participants. Ever use of the examined hair products was not associated with ovarian-cancer incidence, but frequent use of straighteners, relaxers, or pressing products—more than four times in the previous year—was associated with higher incidence. The estimate was based on a relatively small number of outcomes, and the authors described the finding as novel. It raised a signal for study, not a product-specific causal conclusion.

On October 17, 2022, NIH publicized a second Sister Study analysis. Among 33,947 participants with a uterus at enrollment, researchers identified 378 uterine cancers over an average 10.9 years. Compared with never use in the previous year, ever use was associated with a hazard ratio of 1.80, while frequent use was associated with a hazard ratio of 2.55. NIH stressed that more research was needed to confirm the result and identify chemicals that might be involved.

February 2023: the federal cases become MDL 3060

On February 6, 2023, the Judicial Panel on Multidistrict Litigation transferred nine actions to the Northern District of Illinois and noted 44 additional potentially related federal actions. Plaintiffs alleged that use of certain chemical hair relaxer products caused uterine, ovarian, or other hormone-sensitive cancers and that manufacturers failed to warn. Defendants opposed centralization and dispute liability. The Panel found common factual questions about product development, marketing, testing, and the scientific evidence, then assigned the docket to Judge Mary M. Rowland.

The transfer order did not find that all relaxers share one formulation, that the named products cause cancer, or that every person who used a straightener has the same claim. MDL centralization coordinates federal pretrial proceedings. State lawsuits can remain in state court, and federal plaintiffs retain individual product histories, diagnoses, defenses, state-law claims, and limitation questions.

August 2023 to 2024: standardized pleadings and proof collection

Case Management Order 7, entered August 3, 2023, established a master complaint and short-form complaint. The short form lets an individual plaintiff identify defendants, selected products, use periods, injuries, and legal theories without reproducing every general allegation. Incorporating a master complaint creates efficiency; it does not make allegations true or replace the need to prove exposure, diagnosis, causation, and damages.

The court also adopted a plaintiff fact sheet seeking product-use, medical, and background information under oath. Case Management Order 10 in March 2024 set procedures for certain dismissals without prejudice and refiling. These orders help explain why the historical and pending totals can diverge: cases may leave or reenter pending status through procedural mechanisms. Neither order announced a settlement grid, public eligibility test, or universal filing deadline.

2023 research adds an important second cohort

A Black Women's Health Study analysis published in 2023 followed 44,798 Black women with an intact uterus. Its overall estimate for heavy use—at least 15 years and at least five times a year—was 1.18 with a 95% confidence interval from 0.81 to 1.71, which included no association. Among postmenopausal participants, moderate and heavy use estimates were elevated. Premenopausal results were null. That pattern is more nuanced than a headline saying the study simply confirmed or refuted the Sister Study.

The cohorts also measured exposure differently and enrolled different populations and time periods. Both depended substantially on self-reported product use, and neither comprehensively reconstructed every brand, ingredient, or formulation across a lifetime. The litigation will require courts to decide whether particular expert methods are admissible and individual plaintiffs to connect a product history to a diagnosis. Epidemiology informs that work but does not finish it.

July 2026: a very large docket, still in pretrial coordination

JPML reported 11,877 pending actions and 16,059 historical actions in MDL 3060 on July 1, 2026. For comparison, the January 2, 2025 report showed 9,819 pending and 11,613 historical actions. Growth shows sustained filing and administrative load. The gap between historical and pending totals does not disclose how many actions settled, were dismissed, were refiled, or ended for another reason.

Reliable next milestones will come from official orders on discovery, expert evidence, dispositive motions, trial selection, remand, or an agreement actually filed or described by the court. New case counts do not strengthen the science by themselves. Likewise, a new epidemiologic paper may affect expert analysis without resolving every legal element. Any personal review still depends on product and salon records, timing and frequency of use, pathology, treatment history, alternative risk factors, jurisdiction, and applicable law.

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