Study Finds Possible Link Between Hair Straightening Chemicals and Uterine Cancer

Women who use chemical hair straighteners and relaxers may have a higher risk of uterine cancer, according to a new study from researchers at the US National Institutes of Health (NIH).

The study findings were published on October 17, 2022, in the Journal of the National Cancer Institute.

Study details

The researchers used data from more than 33,000 women taking part in the Sister Study, a large, ongoing study looking for risk factors for breast cancer and other health conditions.

At the time the women enrolled in the study, they were asked about their use of different kinds of hair products over the previous year, including hair dyes, straighteners and relaxers, and permanents or body waves.

After an average of nearly 11 years of follow-up, women who had reported using hair straightening products were almost twice as likely to have developed uterine cancer than those who did not, after adjusting for other factors that might affect risk. Women who had reported frequent use of straighteners (more than 4 times in the previous year) were about 2½ times more likely to develop uterine cancer.

The researchers did not find links between uterine cancer and the use of other hair products, including hair dyes, highlights, and perms.

Concerns about hair products and cancer

Data from the Sister Study has been used in the past to look for possible links between hair products and other cancers, especially cancers that grow in response to hormones. This includes breast and ovarian cancer, as well as uterine cancer. (The vast majority of uterine cancers – cancers that start in the uterus – are endometrial cancers, which start in the lining of the uterus.)

Concerns have been raised about possible links between some hair products and these cancers because some of the chemicals used in hair products might be absorbed through the scalp and have estrogen-like properties in the body. Some hair products might also contain other chemicals that have been linked to cancer, such as formaldehyde.

Previous research from the Sister Study has also linked straightener use with a higher risk of breast cancer.

Results might have greater impact for Black women

In the current study, about 60% of the women who reported using straighteners in the previous year self-identified as being Black. While the study didn’t find that the link between straightener use and uterine cancer risk was different by race, the effects may be greater for Black women because they’re more likely to use these products.

“Because Black women use hair straightening or relaxer products more frequently and tend to initiate use at earlier ages than other races and ethnicities, these findings may be even more relevant for them,” said Che-Jung Chang, PhD, one of the authors of the study, in a press release announcing the study results.

Putting the results into context

“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, head of the NIEHS Environment and Cancer Epidemiology group and lead author of the study. “This doubling rate is concerning. However, it is important to put this information into context - uterine cancer is a relatively rare type of cancer.”

Furthermore, while the researchers found a possible link between hair straightener use and uterine cancer, they did not conclude from this study that using these products causes uterine cancer. Further studies on this topic would be needed to confirm and/or clarify this link.

“More research is needed to confirm these findings in different populations, to determine if hair products contribute to health disparities in uterine cancer, and to identify the specific chemicals that may be increasing the risk of cancers in women,” said White.

Lowering your risk

Some women might choose to limit or avoid the use of hair straightening products, based on the limited information available so far. For those who are concerned, there are also other things you can do to help lower your risk of endometrial cancer (the most common type of uterine cancer), such as:

• Getting to and staying at a healthy weight. Being obese (very overweight) has been linked with an increased risk of endometrial cancer.
• Get regular physical activity. Higher levels of physical activity have been linked with lower endometrial cancer risk.