However, in the paper they note that several chemicals found in straighteners (such as parabens, bisphenol A, metals and formaldehyde) could be contributing to the increased uterine cancer risk observed.

Chemical hair straightener lawsuits claim that hair relaxer products made by L'Oreal and other companies cause cancer and other health issues. According to lawsuits, manufacturers failed to warn that their products could increase the risk of uterine, endometrial and ovarian cancer.

The researchers found that those who reported having chemical hair straightening more than four times within a year had 2.5 times higher risk of developing uterine cancer than those who didn't straighten their hair.

Scientists have long identified an association between the use of hair-straightening chemical products with an increased risk of certain hormone-related cancers, including ovarian and breast cancers, and uterine cancer, particularly among Black and Latina women.

Treatments used to straighten or relax hair contain a mixture of chemicals. Some formulations contain the carcinogen formaldehyde as an active ingredient. Several studies have found associations between the use of hair straighteners or relaxers and the subsequent development of breast cancer.

According to researchers, parabens, phthalates, formaldehyde and the toxic chemical DEHP are among the ingredients in relaxers that may cause cancer. For example, a 2022 study found that women who receive chemical hair straightening more than four times a year have twice the risk of developing uterine cancer.

Keratin Straightening Treatment. “A keratin treatment is considered to be the safest way to permanently straighten hair because it does not rely on harsh chemicals as relaxers and permanent waves do.”

Infrared straighteners are the gentlest way to heat your hair, so if you want to cut down on damage, we recommend a fast-acting infrared straightener - like Bio Ionic's 10X Pro Styling Iron. The straightener uses infrared heat, which heats hair from the inside out rather than the outside in.

Women who used hair relaxers at least seven times a year had a 1.4 times higher risk of developing uterine fibroids than those who did not use hair relaxers. The study also found that the risk of developing fibroids increased with the frequency and duration of hair relaxer use.

Investigators concluded that overall, women who used permanent hair dye regularly (every five to eight weeks) were 9% more likely to develop breast cancer than women who didn't use permanent hair dye.

Keratin Straightening Treatment. “A keratin treatment is considered to be the safest way to permanently straighten hair because it does not rely on harsh chemicals as relaxers and permanent waves do.”

Compared to women who didn't use hair-straightening chemicals, women who did use them got uterine cancer more frequently. The difference in the risk went from around 1.6% to over 4%.