Letter Questions Strength of Evidence Linking Hair Relaxers to Uterine Cancer

Key Takeaways

• A recent Letter to the Editor urged caution when interpreting studies linking chemical hair relaxers to uterine cancer.
• The author highlights methodological limitations, including self-reported exposure data, limited product ingredient information, and potential confounding variables.
• While current studies report statistically significant associations, they do not establish causation.

A recently published Letter to the Editor in the Journal of Drugs in Dermatology urged clinicians to interpret the growing body of research examining chemical hair relaxers and uterine cancer with caution, arguing that important methodological limitations prevent current evidence from establishing a causal relationship.

Author Shaveonté Graham, MD, reviewed two frequently cited epidemiologic studies—the 2022 Sister Study and the 2023 Black Women's Health Study—and acknowledges that both identified statistically significant associations between frequent, long-term hair relaxer use and increased uterine cancer risk. However, Dr. Graham noted that several study limitations warrant careful consideration before drawing broader conclusions.

Among the primary concerns are reliance on self-reported hair product use (which introduces recall bias and exposure misclassification), and the absence of detailed information regarding specific product brands or chemical ingredients. The letter also notes that product formulations have changed over time and vary geographically, complicating efforts to identify any individual ingredient associated with risk.

Dr. Graham further questions the generalizability of the available data. The Sister Study largely enrolled women with a family history of breast cancer and included relatively few Black participants, while the Black Women's Health Study focused exclusively on Black women, limiting comparisons across broader populations.

The letter also highlights the potential influence of unmeasured confounders, including diet, occupational exposures, genetic susceptibility, and use of other personal care products.

"Future research must use more precise exposure assessments, track product ingredients, and include broader and more diverse populations," Dr. Graham wrote. "Improved study designs, such as longitudinal or experimental approaches, are needed to better understand the potential public health risks of chemical hair relaxers; if any do exist. Until then, clinicians and consumers must interpret current findings with caution and advocate for greater transparency in cosmetic product safety."

Source

Graham S. Journal of Drugs in Dermatology. 2026;25(7)9682.