A study from the National Institutes of Health (NIH) found a link between uterine cancer and chemical hair straightening products.

The Sister Study, led by the National Institute of Environmental Health Sciences (NIEHS), observed 33,497 women ages 35 to 74 over the course of 11 years to identify risk factors for breast cancer and other health complications. Throughout the study, 378 participants were diagnosed with uterine cancer.

Women who used hair straightening products more than four times in the previous year were more than twice as likely to be diagnosed with uterine cancer compared with those who did not use such products. The report did not find any correlation between cancer and other hair products, such as hair dyes, bleach, highlights or perms.

“We estimated that 1.64% of women who never used hair straighteners would go on to develop uterine cancer by the age of 70; but for frequent users, that risk goes up to 4.05%,” said Alexandra White, PhD, MSPH, head of the NIEHS Environment and Cancer Epidemiology group and the study’s lead author, in a NIH news release. “This doubling rate is concerning. However, it is important to put this information into context—uterine cancer is a relatively rare type of cancer.”

Nearly 60% of the women who reported using straightening products were Black. Study authors attributed this to Black women using straighteners and relaxers more frequently and starting at a younger age compared with women of other races.

The Sister Study attributed the increased risk for uterine cancer in part to chemical exposure from hair products and the absorption of such chemicals through the scalp.

Cancer Health’s Uterine and Endometrial Cancer Basics offers more information on this type of cancer and those at risk (the endometrium is the lining of the uterus; endometrial cancer is the most common type of uterine cancer). The Basics further explains:

More than 61,000 women are diagnosed with uterine cancer and about 11,000 die from it annually, according to the American Cancer Society. Endometrial cancer is much more common; uterine sarcomas account for less than 10% of uterine cancers.


Estrogen is a major risk factor for uterine cancer. Higher estrogen levels over a lifetime—due to early menstruation, late menopause or few or no pregnancies—raise the risk, while use of birth control pills lowers the risk. Women who use hormone replacement therapy after menopause should take a combination of estrogen and progesterone to prevent uterine cancer.


Other risk factors for uterine cancer include family history, genetic factors, obesity, diabetes and a high-fat diet. Using certain types of intrauterine devices for birth control appears to be protective. Certain genetic mutations and pelvic radiation therapy to treat other cancers raise the risk of uterine sarcomas.


Some symptoms to be aware of include:

  • Abnormal vaginal bleeding between periods
  • Vaginal bleeding after menopause
  • Unusual vaginal discharge
  • Lumps in the pelvic area or lower abdomen
  • Pain in the pelvic area or abdomen
  • Unexplained weight loss.

For related articles, click #Uterine Cancer or #Endometrial Cancer. You’ll find headlines such as “Myths and Facts About Gynecologic Cancers,” “IUD Birth Control May Treat Early-Stage Endometrial Cancer,” or “Mindfulness-Based Approach Addresses Sexual Health Concerns After Cancer Treatment.”