Review finds toxic chemicals in hair straightening products, with Black women and stylists hit hardest

Hair straightening products have long been marketed as beauty essentials, but a recent scientific review is adding to a growing body of knowledge about the classes of known toxic chemicals they contain. The findings are especially concerning for Black women, Latina women, and salon workers, whom research suggests may bear the greatest burden.

According to the review, published earlier this month in Current Environmental Health Reports by researchers from Columbia University Mailman School of Public Health, both relaxers and keratin straightening treatments contain several categories of chemicals already known to pose health risks.

Endocrine-disrupting chemicals, carcinogenic chemicals, and heavy metals were identified in all 21 studies and reports included in the review.

Relaxers were most often flagged for fragrance ingredients, along with endocrine-disrupting chemicals such as phthalates and parabens, while keratin treatments most frequently contained formaldehyde, a known carcinogen.

By the end of a shift, salon workers who handled these products had higher urinary levels of toxic chemicals, according to studies examined in the review.

Many people use beauty products regularly without realizing how little is known — or disclosed — about what is in them. But the co-authors noted that the burden is not shared equally. 

Racism has shaped this issue over time and continues to contribute to heavier exposure among Black and Latina women and girls, as well as the salon workers who perform these treatments, who are often women of color themselves.

Companies often are not required to disclose the full chemical makeup of fragrance blends because those formulas are treated as trade secrets. That means a product label may say only "fragrance," even though some of the underlying compounds are themselves endocrine-disrupting chemicals.

Meanwhile, hair products can contain dozens of synthetic chemicals, and some have been linked to hormone disruption, cancer risk, and adverse reproductive outcomes.

The co-authors of the review argued that reducing risk cannot rest only on individuals trying to shop more carefully. Instead, they called for regulatory measures to limit harmful exposure, along with community-led interventions focused on those facing the greatest risk.

Market-based changes could also play an important role. More broadly, the co-authors presented the problem as one of environmental health and equity that needs an institutional response.

"Upstream interventions, including those targeting structural racism and market-based strategies, are needed to reduce environmental exposure and health inequities experienced by communities at risk," they wrote.

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