Products used to straighten hair are associated with an increased risk of uterine cancer, according to a study published on Monday (17).
The findings, published in the Journal of the National Cancer Institute, are especially relevant to black women, who represent the majority of users of straightening products in the United States, and to the so-called “Brazilian straightening”.
Scientists praised the study and called for more research to confirm the findings.
Women who use these products more than four times a year are twice as likely to develop cancer of the uterus, especially endometrial cancer. This disease should not be confused with cervical cancer.
Similar associations were not found in other hair products such as dyes, bleaches, highlights or perms.
“We estimate that 1.64% of women who have never used a hair straightening product will have developed uterine cancer by age 70. But for frequent users, this risk increases to 4.05%”, estimates in a statement Alexandra White, lead author of the study.
“The doubling of this rate is worrying,” he added.
Uterine cancer accounts for about 3% of new cancer cases in the United States, but it is the most common cancer of the female reproductive system. The prognosis is usually good if caught early, but treatment usually involves removing the uterus, which would make pregnancy impossible.
The study is based on data from 33,500 American women, followed for nearly 11 years.
Because black women use these products more often and tend to start out younger, “these results may be of particular interest to them,” said Che-Jung Chang, co-author of the research.
Approximately 60% of women who said they used hair straightening products in the past year identified as black.
Brazilian straightening
“What’s worrisome is that there are chemicals in these products that essentially act like estrogen in the body,” White said. This action disrupts normal hormonal processes, and this can influence cancer risk.
The second possibility raised is that some products have carcinogenic substances, such as formaldehyde, to break the bonds between the hair’s keratin proteins, altering its structure and straightening it.
The keratin treatment known as “Brazilian straightening” was popular when women enrolled in this study between 2003 and 2009. However, its use has declined considerably since then.
The worrying thing is that there are chemicals in these products that essentially act like estrogen in the body.
The researchers did not collect information about specific products and brands, but they point out that various chemicals present in these types of products may contribute to an increased risk of cancer. In addition to formaldehyde, popularly known as formaldehyde, the study also cites parabens, bisphenol A and metals.
Compared to other categories, hair straightening products can promote the absorption of chemicals through injuries or burns to the scalp, or through the use of flat irons, whose heat breaks down the substances, the study points out.
Other studies have already established a link between straighteners and an increased risk of breast cancer.
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