New research from the National Institutes of Health (NIH) suggests that women who use hair straightening or relaxing products may face a higher risk of several non-reproductive cancers. An analysis of more than 46,000 U.S. women enrolled in the NIH-led Sister Study found increased rates of pancreatic cancer, thyroid cancer, and non-Hodgkin’s lymphoma among users of these products.

According to the study, women who reported using hair straighteners or relaxers were more than twice as likely to develop pancreatic cancer, 70% more likely to develop thyroid cancer, and 60% more likely to develop non-Hodgkin’s lymphoma compared with non-users. Participants were surveyed about product use between 2003 and 2009 and reported cancer diagnoses an average of 13 years later. Some of these products are known to release hormone-disrupting chemicals or carcinogens, including formaldehyde.

Previous Sister Study findings linked hair straightening products to hormonally sensitive cancers such as breast, uterine, and ovarian cancer. This new analysis expands concerns to a broader range of cancers. While Black women are the most frequent users of these products, researchers say there were too few cases to fully assess differences in risk by race or ethnicity. NIH scientists emphasize the need for further research to identify which ingredients may drive these risks and whether certain life stages are especially vulnerable to exposure.