Hair straighteners’ risk too small for docs to advise against their use


Not ready to go curly

Ms. Ghazi said she decided to stop using keratin straighteners years ago after she learned they are made with several added ingredients. That includes the chemical formaldehyde, a known carcinogen, according to the American Cancer Society.

“People have been relaxing their hair for a very long time, and I feel more comfortable using [a relaxer] to straighten my hair than any of the others out there,” Ms. Ghazi said.

Janaki Ram, who has had her hair chemically straightened several times, said the findings have not made her worried that straightening will cause her to get uterine cancer specifically, but that they are a reminder that the chemicals in these products could harm her in some other way.

She said the new study findings, her knowledge of the damage straightening causes to hair, and the lengthy amount of time receiving a keratin treatment takes will lead her to reduce the frequency with which she gets her hair straightened.

“Going forward, I will have this done once a year instead of twice a year,” she said.

Dr. White, the author of the paper, said in an interview that the takeaway for consumers is that women who reported frequent use of hair straighteners/relaxers and pressing products were more than twice as likely to go on to develop uterine cancer compared to women who reported no use of these products in the previous year.

“However, uterine cancer is relatively rare, so these increases in risks are small,” she said. “Less frequent use of these products was not as strongly associated with risk, suggesting that decreasing use may be an option to reduce harmful exposure. Black women were the most frequent users of these products and therefore these findings are more relevant for Black women.”

In a statement, Dr. White noted, “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%.”

The findings were based on the Sister Study, which enrolled women living in the United States, including Puerto Rico, between 2003 and 2009. Participants needed to have at least one sister who had been diagnosed with breast cancer, been breast cancer-free themselves, and aged 35-74 years. Women who reported a diagnosis of uterine cancer before enrollment, had an uncertain uterine cancer history, or had a hysterectomy were excluded from the study.

The researchers examined hair product usage and uterine cancer incidence during an 11-year period among 33 ,947 women. The analysis controlled for variables such as age, race, and risk factors. At baseline, participants were asked to complete a questionnaire on hair products use in the previous 12 months.

“One of the original aims of the study was to better understand the environmental and genetic causes of breast cancer, but we are also interested in studying ovarian cancer, uterine cancer, and many other cancers and chronic diseases,” Dr. White said.

A version of this article first appeared on WebMD.com.


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