Systematic Review of the Epidemiology of Hair Relaxer Use and Hormone-Sensitive Reproductive Outcomes Among Black Adult Women in the United States

Hair relaxers are predominantly used by Black women in the United States. It has been recently suggested that exposure to potential endocrine-disrupting compounds from the use of these products may be associated with the development of gynecological and breast cancers and anatomically relevant nonmalignancies. We conducted a systematic literature review using PubMed to identify original studies reporting measures of association between hair relaxer use and relevant adverse outcomes, focusing specifically on Black women in the United States. A total of 1382 studies were initially identified, and after consideration of the exclusion and inclusion criteria, the final set of studies consisted of seven cohort studies and one case-control study. The overall findings suggest that Black women in the United States do not experience an increased risk of breast cancer, ovarian cancer, or uterine cancer due to hair relaxers. One study found a statistically significant association between hair relaxer use and uterine leiomyomata, but there were no other studies identified to support these findings. None of the studies characterized the chemical constituents of hair relaxers. From an epidemiologic perspective, the weight of the evidence does not support the hypothesis that the use of hair relaxers is a risk factor for gynecological and breast cancers in US Black women.