A new study has found that chemicals used in hair-straightening treatments may increase the risk of developing several cancers by up to 166%, raising concerns about the carcinogenic formaldehyde present in chemical hair-smoothing products, including keratin treatments and hair-styling tools.

Study Details:
Researchers from Emory University in Georgia analyzed long-term health data from over 50,000 American women aged 35–74, with no personal history of breast cancer but at least one family member diagnosed with the disease.

Over an average follow-up period of 13.1 years, data from 46,287 women were included. The study focused on cancers reported in at least 100 cases and assessed participants’ use of hair-straightening tools or relaxers in the 12 months prior to joining the study.

Study Results:

Women using hair-straightening products were 166% more likely to develop pancreatic cancer.

Thyroid cancer risk increased by 71%.

Non-Hodgkin’s lymphoma risk increased by 62%.

Risks were higher among frequent users, defined as those using products more than four times per year.

Researchers warned against frequent use of hair-straightening products without awareness of potential health risks, emphasizing that repeated exposure to these chemicals may have long-term health consequences, particularly given the lack of early detection tests for cancers such as pancreatic cancer.