Hair Relaxer & Straighteners Linked to Cancer

The Link Between Chemical Hair Relaxer Products & Uterine Cancer

An NIH-funded study published in October 2022 found an association between women who regularly used chemical hair relaxer products and uterine cancer:

Participants who used hair relaxers were at an elevated risk of developing uterine cancer (endometrial cancer and uterine sarcoma) compared to participants who did not use hair relaxers; AND 

Participants who used hair relaxers more than four times per year more than two and half times (>2.5x) more likely to develop uterine cancer than participants who did not use relaxers as often. 

The study also warned that negative health impacts associated with using relaxers had the potential to impact Black and/or African American women more than women who identify with other races and ethnicities:

An earlier report from the same study found that frequent users of hair relaxers were more than 2x as likely to develop ovarian cancer.

How Does Chemical Hair Straightening Work?

Chemical hair straightening works by using heat and chemicals to break down the natural bonds in hair. Three types of these bonds are disulfide, hydrogen and salt bonds.

When people apply chemical hair straighteners to hair, they break disulfide bonds. This allows the hair to be straightened. It typically lasts until hair grows out.

Chemicals in hair straighteners include sodium hydroxide, ammonium thioglycolate, sodium thioglycolate, formaldehyde, cyclosiloxanes, parabens, diethanolamine, phthalates, benzophenone-3 and triclosan.

What Injuries have been associated with Hair Relaxer and Chemical Straighteners?

The main injuries associated with Hair Relaxer and Chemical Straighteners are:

• Ovarian Cancer
• Endometrial Cancer
• Uterine Cancer
• Uterine Fibroids

Uterine cancer and breast cancer are the top two cancers linked to hair straighteners. Researchers have found that endocrine disrupting chemicals, or EDCs, in chemical hair straighteners are to blame for an increased cancer risk.

In addition to cancer, studies have also linked chemical hair straighteners to endometriosis and uterine fibroids.

According to researchers, women who use the products more than four times a year, or every five to eight weeks, have the greatest risk of developing uterine or breast cancer.