Hair Straighteners May Increase Risk of Uterine Cancer in Women: Study

Regular exposure to chemicals in hair relaxer may cause uterine cancer, with risk significantly higher among African American women

The findings of a new study highlight growing concerns in recent years about the safety of chemicals in hair straightener products, indicating that there may be a link between hair relaxer and uterine cancer for certain women.

Chemical hair straighteners have become increasingly popular among U.S. women in recent years, to style hair into a straight configuration by using extremely high heat and chemicals to break down Disulphide bonds, which are the permanent hair bonds responsible for an individual’s natural hair type. However, the products often use a variety of chemicals, one of which is often formaldehyde, a known human carcinogen.

In a report published this week in the Journal of the National Cancer Institute, researchers with the National Institute of Environmental Health warn that ingredients used in hair straighteners may cause uterine cancer, as they often contain hazardous chemicals with endocrine-disrupting and carcinogenic properties.

In recent years multiple studies have been published that suggest a possible link between chemical hair relaxers and cancers, including breast cancer, ovarian cancer, and other hormone-related cancers. However, this new cohort study is the first to identify uterine cancer risks from hair straightener product exposure.

Uterine Cancer Risk from Hair Relaxer and Straighteners

In the latest study, researchers reviewed data on nearly 34,000 women in the United States between the ages of 35 and 74 who completed questionnaires on their use of multiple hair products, including hair dyes, straighteners, relaxers, or pressing products, and permanents or body waves. A 10 year follow-up on the incident rate of uterine cancer diagnosis was performed.

According to the results, researchers identified 378 uterine cancer cases, finding participants who used straightening products at least once had the highest rate of uterine cancer diagnosis compared to any other hair products involved in the study. They also had a higher rate of uterine cancer when compared to women who used no hair straightener products.

Within the last 12 months of the study period, researchers reported that 4% of women who frequently used hair straightener chemical products developed uterine cancer by age 70, while only 1.6% who never used the products developed uterine cancer. Researchers noted the risk of uterine cancer from chemical hair straighteners was significantly higher among African American women, making up only 7.4% of study participants, but accounted for 59.9% of those reporting use of the chemical straighteners.

While individual product brands of chemical hair straightener products were not named in the study, researchers stated the significant increase in uterine cancer among chemical straightener warrants additional research to explore a potential causal link and regulatory action to remove or limit the use of harmful chemicals.

Chemical Hair Relaxer Side Effects

A 2019 study published in the International Journal of Cancer (IJC) issued similar findings, indicating women who reported regularly using straighteners and permanent hair dyes were 9% more likely to develop breast cancer than non-users.

Researchers from National Institute of Environmental Health Sciences (NIEHS) collected data from the Sister Study, which is a long-term research project in the U.S. and Puerto Rico involving over 50,000 participants to study how the environment and genes affect women’s chances of getting breast cancer.

Over an eight year period, researchers identified 2,794 cases of breast cancer after chemical hair straighteners use. The study revealed those who frequently used hair straightener products were at a significantly increased risk of breast cancer, finding women using hair straighteners at least every five to eight weeks, had a 30% increased risk of developing breast cancer.

Researchers pinpointed that African American women who reported using permanent hair dyes regularly were associated with a 60% increase of breast cancer diagnosis, compared to an 8% increased risk for Caucasian women.