Chemical Hair Straighteners & Cancer Risks

Recent medical studies link chemical hair straighteners and cancer, especially uterine cancer. Certain chemicals in hair relaxers are carcinogens and disrupt the reproductive system and may increase the risk of cancer. Black women are heavy users of these products and experience the highest risk.

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Last Modified: April 2, 2024
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Which Chemicals in Hair Straighteners Cause Cancer?

Researchers have linked endocrine-disrupting chemicals, including parabens, metals, bisphenol A and formaldehyde contained in many hair straightening products, to the risk of developing cancer.

For example, a 2022 study from the National Institutes of Health found that the risk of uterine cancer doubles in women who use chemical hair straighteners more than four times per year.

Chemicals Found in Hair Straighteners and Associated with Cancer

  • Bisphenol A
  • Formaldehyde (methylene glycol and formalin)
  • Metals
  • Parabens

Researchers in the 2022 study didn’t investigate specific brands or ingredients in hair products, but they acknowledged that several chemicals commonly found in chemical hair straighteners create a higher risk of uterine cancer.

Keep in mind that not every person who uses hair relaxers will develop cancer. For example, professional hair stylist Tonya Herrell told Drugwatch that she has clients and family that have been using hair relaxers for years, and they have not developed cancer. 

“In all my years dealing with relaxers, I have never encountered a case where the relaxer is a direct cause of their cancer. My relatives and aunties have been getting them for years,” Herrell said. 

How Do These Chemicals Increase Cancer Risk?

Scientists theorize that chemicals in hair relaxers can affect hormones in the body and lead to hormone-related cancers, such as uterine, ovarian and breast cancer. A further NIH study also examined potential links between hair products and other cancers, particularly those that develop in response to hormones, including ovarian cancer, breast cancer and uterine cancer.

Medical professionals raised concerns about the possibility of ingredients in hair relaxers getting absorbed through the scalp and having estrogen-like properties in the body.

“Research is still developing as to exactly how hair straightening products and the toxic substances within them cause cancer. But hair relaxers or straighteners may cause lesions or burns on the scalp. It is currently believed that these injuries may make it easier for the endocrine-disrupting chemicals (EDCs) and other toxic chemicals to enter the body,” said Moshe Horn, an attorney with Simmons Hanly Conroy who has been litigating these cases and is familiar with the science of hair relaxer cases.


Heat usually activates chemical straightening solutions. When a stylist heats the solution, formaldehyde in the products gets released into the air as a gas. The International Agency for Research on Cancer identifies formaldehyde as a human carcinogen based on leukemia and nasopharyngeal studies.


This group of chemicals, often used as preservatives in cosmetics products, has a high endocrine-disruption capacity. They disturb the hormones and reproductive systems of men and women and increase the risk of cancer.

Bisphenol A

This chemical can interact with estrogen receptors, a likely reason why receptors can trigger the development of multiple cancers. Exposure to heavy metals, including cadmium, arsenic, nickel and chromium, all classified as group 1 carcinogens, can induce cell damage and other changes that result in an increased risk of cancer.

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Cancers Associated With Chemical Hair Straighteners

Permanent chemical hair straighteners and other hair products are most strongly associated with hormone-sensitive cancers, including health risks like uterine, breast and ovarian cancers. So far, studies show uterine cancer is the most strongly linked to hair relaxers.

Researchers discovered that some chemicals in chemical straighteners, including parabens and phthalates, get absorbed through the skin and disrupt the endocrine system. Another common ingredient, formaldehyde, is a known human carcinogen. Studies show that the toxic chemical damages human DNA and scientists have linked it to myeloid leukemia.

Findings from the 2022 NIH study provided the first epidemiological evidence of the link between the use of chemical hair straightening treatments and uterine cancer. Women who applied chemical straighteners more than four times a year had more than double the risk of uterine cancer.

Uterine Cancer

After the 2022 NIH study finding on uterine cancer, a December 2023 published in Environmental Research found postmenopausal Black women who said they used hair relaxers more than twice a year for more than five years had at least a 50% increase in their risk of developing uterine cancer.

Daniel A. Landau, M.D.
Dr. Daniel Landau Oncologist

Dr. Daniel Landau, section chief of hematology and oncology at Orlando Health Cancer Institute, discusses the findings of the 2022 NIH study by Che-Jung Chang and colleagues that linked chemical hair straighteners to double the risk of uterine cancer. He also talks about uterine cancer and its warning signs.

What did the 2022 NIH study find?

In a study looking at potential risk factors, chemical hair straightener use seemed to correlate with the likelihood of the development of uterine cancer, especially in the African American population. In a study of more than 30,000 women, frequent chemical hair straightener use more than doubled the likelihood of the development of uterine cancer. Fortunately, the risk was low across the entire group, but chemical hair straighteners seem to be a risk factor.

How do chemical hair straighteners increase uterine cancer risk?

Uterine cancers often have a hormonal link to them. Elevated estrogen seems to increase the likelihood of the development of uterine cancers. It is hypothesized that some of the chemicals found in these products (such as phthalates, parabens and cyclosiloxanes) can essentially behave like hormones in the body. It is thought that this is why the risk may increase when these chemicals are introduced. The skin of the scalp can absorb this and have it enter the bloodstream.

What are the warning signs of uterine cancer?

Uterine cancer remains rare. But warning signs of uterine cancer include vaginal bleeding, pain with intercourse, pelvic pain, vaginal discharge, frequent urination and anemia.

Ovarian Cancer

In one 2021 study published in Carcinogenesis, researchers followed more than 200 women for 10 years and found that frequent use — more than four times in a year — was associated with an increased risk of ovarian cancer.

Breast Cancer

An NIH study published in the International Journal of Cancer showed that women who used chemical straighteners had a higher risk of developing breast cancer than those who didn’t — and a 30% increased breast cancer risk if they used them every five to eight weeks.

Michele Lynn developed breast cancer after decades of using hair relaxers, her husband Mike told Drugwatch. Mike didn’t realize there was a link between Michele’s cancer and chemical hair straighteners until after she passed at age 43.

“She was always very healthy and very fit,” Mike said, baffled by Michele’s cancer diagnosis. “She never smoked, wasn’t a heavy drinker and wasn’t overweight. When she was diagnosed, the BRCA test showed she wasn’t a gene carrier, so it wouldn’t affect our daughter.”

Which Hair Straightening Brands Are Linked To Cancer?

Researchers from the 2022 study that connected chemical hair straightening treatments to cancer didn’t collect information on specific brands and ingredients in chemical hair straighteners. However, they listed parabens, phthalates (including bisphenol A), formaldehyde and metals, which are common in chemical hair straighteners, as chemicals that can cause cancer.

While there is no definitive collection of brands that are linked to cancer, people who developed cancer filed chemical hair straightener lawsuits and claimed the brands they used caused them to develop cancer.

Hair Straightening Brands Linked To Cancer Litigation
  • Dark and Lovely
  • Just for Me
  • L’Oréal
  • Motions
  • Namaste
  • Olive Oil Girls
  • Optimum
  • Soft & Beautiful
  • Strength of Nature Global LLC
  • TCB Naturals

It’s important to note that researchers are still studying the link between chemical hair straighteners and cancer. Researchers need more studies and data.

Currently, lawyers are accepting cases from people who developed uterine, endometrial and ovarian cancer because the science for these cancers is the strongest.

Black Women Have Greater Risk of Cancer From Hair Relaxers

Studies have shown that Black women have a greater risk of developing cancer from hair relaxer use because they are typically heavy users. Sixty percent of the participants in the 2022 NIH study who reported using chemical hair straighteners were Black women, leading researchers to conclude that the exposure burden was higher among that demographic.

According to Kimberly Bertrand, associate professor of medicine at Boston University Chobanian & Avedisian School of Medicine and one of the authors in the 2023 study in Environmental Research, up to 95% of self-identified Black women had used hair relaxers.

“Compared to non-Hispanic white women, Black women have higher rates of aggressive subtypes of uterine cancer and are nearly twice as likely to die from their disease.”
Kimberly Bertrand Associate professor of medicine at Boston University Chobanian & Avedisian School of Medicine

Some Black women also claim that manufacturers marketed hair straighteners to Black women, whose naturally curly hair made them potential buyers, and many of these consumers have filed chemical hair straightener lawsuits.

“It appears that Black women are in greater danger than women of other demographics,” said Horn.

Please seek the advice of a medical professional before making health care decisions.