Are Relaxers Putting Black Women’s Health at Risk?

The Sister Study followed women aged 35 to 74 who had no personal history of breast cancer but had at least one sister diagnosed with the disease. Enrollment ran from 2003 to 2009, with participants tracked through September 2021.

For this analysis, researchers reviewed data from 46,287 women who were followed for an average of 13 years. They examined whether participants had used chemical hair straighteners or relaxers in the 12 months before joining the study and tracked cancer diagnoses over time.

What is Formaldehyde and Why is it A Risk?

Formaldehyde, often used as a preservative in these products, can “off-gas” over time—releasing fumes, especially when heated. Repeated exposure to these fumes can cause eye and throat irritation, breathing issues, and over time, may increase the risk of head, neck, and blood cancers.

These risks are intensified when products are applied in poorly ventilated areas like small bathrooms or salons without adequate airflow.

The American Cancer Society has previously warned that formaldehyde exposure is linked to cancers of the nose, upper throat, and stomach, and may also increase the risk of leukemia.

When relaxers and straightening treatments are heated during application, formaldehyde escapes as a gas through a process called “off-gassing.” The Department of Health and Human Services lists formaldehyde as a “known carcinogen”. Repeated inhalation can cause immediate effects like eye and respiratory irritation, but the long-term concerns include increased cancer risk.

In 2022, researchers at the National Institutes of Health released a study showing that women who never used hair straighteners had a 1.64% chance of developing uterine cancer by age 70, but for frequent users, that risk increased to 4.05%.