This article provides educational information. It is not legal advice and does not create an attorney-client relationship. Consult with a qualified attorney regarding your specific situation.
The hair relaxer lawsuits rest on a growing body of scientific research connecting the chemicals in these products to an elevated risk of reproductive cancers. Understanding that science is essential to understanding the litigation and the legal claims women across the country are pursuing.
The Chemicals of Concern
Chemical hair relaxers contain ingredients classified as endocrine-disrupting chemicals, substances that interfere with the body's hormonal system by mimicking, blocking, or altering normal hormone function. Specific chemicals identified in relaxer formulations include parabens, phthalates, formaldehyde and formaldehyde-releasing compounds, and bisphenol A. Because uterine, endometrial, and ovarian cancers are hormone-sensitive, disruption of normal estrogen signaling can increase the conditions under which these cancers develop.
The method of application matters as well. Relaxers are applied directly to the scalp, which has higher absorption capacity than other skin surfaces, and are left in contact for extended periods. This means chemicals enter the body at greater concentrations than many other topically applied products.
The 2022 Sister Study
The most significant study underlying the litigation was published in the Journal of the National Cancer Institute in 2022 using data from the National Institutes of Health Sister Study, which enrolled more than 50,000 women. Researchers found that women who used chemical hair straighteners more than four times per year were more than twice as likely to develop uterine cancer. The association was specific to chemical straighteners. No elevated risk was found for hair dye, bleach, or highlights. The findings were particularly pronounced among Black women, who have historically used these products at higher rates and who also experience disproportionately higher rates of uterine cancer.
Prior and Subsequent Research
The 2022 findings built on prior research examining potential links between hair product chemical exposure and ovarian cancer, breast cancer, and uterine fibroids. Subsequent studies have continued to explore associations with endometrial and ovarian cancer. The accumulation of consistent findings across multiple independent studies strengthens the scientific foundation supporting the litigation, while also underscoring that research continues and causation at the individual level remains a central issue in each case.
How Science Functions in the Courtroom
In mass tort litigation, scientific evidence operates at two levels. General causation addresses whether the chemicals at issue are capable of causing the type of harm alleged. Specific causation addresses whether a particular plaintiff's cancer was caused by their exposure to the defendant's product. Expert witnesses on both sides present competing scientific positions, and the court determines which expert testimony meets the legal standards for admissibility. In the hair relaxer MDL, the court has scheduled a Science Day for this purpose, allowing both parties to present their scientific evidence before key rulings are made.
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