The hazards of hair extensions

Most women use hair extensions these days. However, in the most comprehensive analysis to date, a new study by Silent Spring Institute identified dozens of hazardous chemicals in hair extensions, including products made from human hair, providing the strongest evidence yet of the potential health risks associated with this largely unregulated category of beauty products that  affect women.

Published in Environment & Health, the study arrives amid growing concern about the health impacts of hair extensions.

While prior reports have found some chemicals of concern in hair extensions, there's still much we don't know about their overall chemical makeup. This is an industry that has long overlooked the health of  women, who should not have to choose between cultural expression, convenience, beauty and their health.

Hair extensions can be made from synthetic fibers and bio-based materials, including human hair, and are often treated with chemicals to make them flame resistant, waterproof, or antimicrobial.

Yet, companies rarely disclose the chemicals used to achieve these properties, leaving consumers in the dark about the health risks from prolonged wear. The fibers sit directly on the scalp and neck, and when heated and styled, they can release chemicals into the air that wearers may breathe in.

For the study, researchers purchased 43 popular hair extension products online and from local beauty supply stores. They categorized the products by fiber type—synthetic (mostly plastic polymers) or bio-based (including human, banana or silk)—and then coded them by their claims. Nineteen of the synthetic samples claimed to be flame retardant, three were water resistant, nine heat resistant, and three carried "green" claims such as "no PVC" or "non-toxic."

The researchers used a technique called non-target3ed analysis to screen the samples for a wide range of chemicals, including compounds that are not typically tested for in products.

Using two-dimensional gas chromatography with high-resolution mass spectrometry, the team detected over 900 chemical signatures, capturing both known and unknown substances. Machine-learning software was then used to match these signatures to a chemical library, ultimately identifying 169 chemicals across nine major structural classes.

The analysis revealed dozens of hazardous substances linked with cancer, hormone disruption, developmental problems, and effects on the immune system. These included flame retardants, phthalates, pesticides, styrene, tetrachloroethane, and organotins.

Key findings:

• All but two samples contained hazardous chemicals, and both of those were labeled as "non-toxic" or "toxic-free."
• 48 chemicals appeared on major hazard lists,  65 for causing cancer, birth defects, or reproductive harm.
• Four flame retardants were found in both synthetic and bio-based samples.
• 17 chemicals related to breast cancer were found across 36 samples, including compounds known to alter hormones in ways that increase risk.
• Nearly 10% of samples contained toxic organotins, some at concentrations exceeding health-based levels set in the European Union, where the chemicals are regulated.

Organotins are commonly used as heat stabilizers in PVC and have been linked with skin irritation, which is a common complaint among hair extension users." Organotins have also been linked with cancer and hormone disruption.

With the global hair extension market projected to surpass $14 billion by 2028, these findings make clear that stronger oversight is urgently needed to protect consumers and push companies to invest in making safer products.

Identifying chemicals of health concern in hair extensions using suspect screening and non-targeted analysis, Environment & Health (2026). DOI: 10.1021/envhealth.5c00549