New Study Finds Chemical Hair Straighteners Increase The Risk of Uterine Cancer

Chemical Hair Straightner

There’s a new study released in the US which links uterine cancer and the use of chemical hair straighteners – or relaxers. For almost 11 years, researchers at the US National Institute of Environmental Health Sciences (NIEHS) has followed 33,947 adults and monitored their health for the study.

The study found those who’d used a chemical straightening product more than four times in the 12 months prior to being surveyed were 155% more likely to be diagnosed with uterine cancer later, compared with those who had never received a straightening treatment.

To put it in perspective, those who never used hair straightening products would have a 1.64% chance of being diagnosed with uterine cancer by their 70th birthday. This number creeps up to 4.05% for those who frequently straighten their hair using chemicals. While this percentage is still small – it does mean there’s an appreciably higher risk after using these chemicals.


The worrisome results are the latest from a recent string of studies on widely-used chemicals which disrupt the endocrine system. Our endocrine system sends out the messenger chemicals in our bodies which connect hormones to their target organs. If our endocrine system isn’t working correctly, there’s a range of processes which won’t happen.

In 2018, researchers found endocrine-disrupting chemicals in 18 tested hair products. What’s more, 84% of the chemicals identified were not listed on the product labels. Plus 11 products contained chemicals prohibited under the  European Union’s Cosmetics Directive or regulated under California law.

Currently, federal regulations in the US require testing for estrogen receptor activity only when it comes to pesticides and drinking water contaminants. Hair products are left out and this could be having a serious affect on the public’s health.

Other cancers already linked to hair dye and straightening chemicals

In 2019, a study funded by the NIH found permanent hair dye and straightening chemicals are associated with a higher risk of breast cancer, especially among black women who tend to receive these treatments more often.

In 2021, a follow-up study found permanent hair dye and straightening chemicals are also associated with a higher risk of ovarian cancer. Now, uterine cancer can be added to the list as well. The study on this latest type of cancer did not identify differences between racial and ethnic groups, but the authors note that because black women use straightening products at younger ages, higher rates, and higher concentrations, the hazards may be greater.

A 2019 study found that 89% of African American women reported using chemical relaxers or straighteners. Researchers at the NIH are still working out which specific chemicals in hair products can explain the associated carcinogenic effects, but parabens, pthalates, and formaldehydes are some of the leading suspects. The human scalp readily absorbs chemicals which might not make it through thicker areas of skin such as the palms or abdomen.

Flat ironing or blow drying could also thermally decompose chemicals on the hair, leading to potentially more hazardous effects. As well, the authors of the study found a link between the amount of physical activity women undertook and the risk of uterine cancer. The authors wrote: “We observed stronger associations with straightener use among women with low physical activity. Because physical activity has been associated with decreased sex steroid hormones and less chronic inflammation, women with higher physical activity might be less susceptible to other risk factors for uterine cancer. However, more studies are warranted to understand the interrelationship between physical activity, hair product use, and uterine cancer.”

Roughly half of all women in the US have used permanent hair dye at some point, and smoothing keratin treatments and Brazilian blowouts are growing more popular. It seems to us that hairdressers and their clients need to know what these products are doing to their health. We need to carry out studies like this in Australia and see what the figures are like for women in Australia.

Here are some tips which can help you minimise the negative effect of using hair dyes:

  • Always perform a skin patch test before you use the product. Apply a small amount of the dye on the inside of your elbow or behind the ear and leave uncovered for two days. If there is any sign of irritation, do not use the product.
  • Always follow the manufacturer’s instructions and wear gloves.
  • Try to avoid the scalp when applying the dye .
  • Dye your hair in a well-ventilated area preferably with an air purifier (fitted with a carbon and HEPA filter).
  • Do not leave the dye on your head any longer than necessary.
  • Rinse your hair well with water after using the dye.
  • Never mix different hair dye products.
  • Healthier brands are listed on the Environmental Working Group’s website here –

To read the recent study about the link between chemical hair straighteners, you can visit here in the Journal of the National Cancer Institute.

For more information from ACES on how to avoid toxic overload, visit here.

Tips to reduce your toxic load this EARTH DAY