Chemical hair straighteners pose higher uterine cancer risk, unveils US-wide study

18 Oct 2022 --- Women who use chemical hair straightening products have a higher chance of developing uterine cancer than women who did not disclose using these products, according to a National Institutes of Health (NIH) study.

Although there was no correlation between races, the researchers found that many Black women admitted to using chemical hair straighteners and so are likely to be more susceptible to negative health impacts.

The study revealed that other hair products, such as hair dyes, bleach, highlights and perms that the women reported using, were not linked to uterine cancer.

Compared to women who did not use hair straightening products, frequent users were more than twice as likely to later develop uterine cancer. The study classified women who use these straightening products more than four times a year as “frequent users.”

Dr. Alexandra White, head of the NIEHS Environment and Cancer Epidemiology group and lead author of the study highlights that the “doubling rate is concerning.”

“To our knowledge, this is the first epidemiologic study that examined the relationship between straightener use and uterine cancer.”Dr. Chang says these findings may be more relevant to black women because they tend to use straightening products more.

The sister study
The study data includes 33,497 US-based women between the ages of 35 and 74 who took part in the study to find the causes of breast cancer and other illnesses. The investigation is called the Sister Study and was conducted by the National Institute of Environmental Health Sciences (NIEHS), a division of the NIH.

“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%,” says White.

During the nearly 11-year period when the women were monitored, 378 new incidences of uterine cancer were identified.

With 65,950 expected new cases in 2022, uterine cancer is the most prevalent cancer of the female reproductive system and accounts for nearly 3% of all new cancer cases. 

Additionally, research indicates that uterine cancer incidence rates have been rising in the US, especially among black women.

Curls and culture
According to the study published in the Journal of the National Cancer Institute, self-identified black women made up almost 60% of the individuals who admitted to using straighteners in the previous year.

Although the study found no differences in the incidence of uterine cancer according to race, the negative health impacts may be more severe for black women due to the higher prevalence of usage.White says the likelihood of developing uterine cancer because of the products is concerning, but that uterine cancer is relatively uncommon.

“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,” says Dr. Che-Jung Chang, an author of the study and a research fellow in the NIEHS Epidemiology Branch.

Consistently questionable chemicals
The results are in line with earlier research that suggested women’s use of hair straighteners may raise their chance of developing cancers linked to hormones.

The authors of the article point out that a number of chemicals, including parabens, bisphenol A, metals and formaldehyde that have been discovered in straighteners may be contributing to the elevated risk of uterine cancer.

Due to increased scalp absorption from using hair products – which may be aggravated by burns and cuts from using them – chemical exposure from using hair products, especially straighteners, may be more worrying than from using other personal care items.

“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,” White concludes.

By Mieke Meintjes