Straightening products used to straighten hair, especially by black women, pose an increased risk of uterine cancer, according to a large new study from the US Institutes of Health.
Women who frequently use these products – more than four times a year – see their risk of developing uterine cancer more than double, according to this work.
Independent experts have praised the usefulness of this research on a subject that has so far been little studied, and published Monday in the Journal of the National Cancer Institute. They invoked a “precautionary principle” to call for more regulations, although further studies are needed to investigate these findings further.
Uterine cancer (not to be confused with cervical cancer) is a relatively rare form of cancer. It accounts for about 3% of new cancer cases in the United States, with some 66,000 cases and 12,500 deaths in 2022.
But the incidence rates of this cancer are on the rise in the United States, especially among black women.
The study is based on data from nearly 33,500 American women, recruited between 2003 and 2009 and followed for almost eleven years. A total of 378 women developed uterine cancer.
For women who have never used hair straightening products, the risk of developing uterine cancer by their 70s is 1.64%, compared to 4.05% for frequent users, detailed in a press release Alexandra White, lead author of the study.
“Because black women use hair straightening or hair straightening products more frequently and tend to start younger…these results could be of particular interest to them.“, underlined Che-Jung Chang, co-author of this work.
As part of this study, about 60% of women who said they used hair straightening products during the year declared themselves to be black.
The researchers did not collect information on the specific products and brands used.
But they note that several frequently used chemicals could contribute to the increase in the risk of cancer: parabens, bisphenol A, metals or even formaldehyde.
Formaldehyde, commonly known as formaldehyde, can be used in particular for so-called Brazilian smoothing – at limited rates in certain countries, including France. It is classified as a carcinogen.
Another potential mode of action could be the disruption of hormonal mechanisms.
“We know that these smoothing products contain many chemicals, including endocrine disruptors, and they can be expected to have an impact on hormone-dependent cancers”explained to AFP Alexandra White. “The concern is that these items contain chemicals that could act like estrogen in the body.“, she added.
Previous work carried out by the researcher had already raised a link between relaxer products and an increased risk of breast and ovarian cancer.
During the study, no similar association between uterine cancer and other techniques such as dyes, bleaches or permanents was observed.
Hair straightening products could promote the absorption of chemicals via lesions or burns caused to the scalp, or by the joint use of straightening irons whose heat breaks down the chemicals.
In a comment published simultaneously, experts judged that it was “time to intervene”.
Changes “regarding personal care products are likely required on many levels”they wrote, in particular in order to “challenging racialized beauty standards”and at “lack of transparency on chemicals” used.