A recent study by the Silent Spring Institute has mapped a surprising array of potentially toxic substances hidden inside many hair‑extension products, including those made from human hair. This is the most comprehensive chemical screening of these largely unregulated beauty items to date, and the researchers say the data point to real health risks—especially for Black women, who use extensions far more often than other groups.
The findings were published in the journal Environment & Health of the American Chemical Society, adding weight to growing concerns about the long‑term safety of hair extensions. More than 70 % of Black women report wearing extensions at least once a year, compared with under 10 % of women from other racial or ethnic backgrounds. Extensions are popular for cultural expression, personal style, and convenience.
Chemical Treatments and Limited Ingredient Disclosure
Extensions are manufactured from synthetic polymers or bio‑based fibers such as human hair, banana fibers or silk. To give the strands flame resistance, water repellency or antimicrobial properties, manufacturers treat them with a cocktail of chemicals. Yet, product labels rarely list these additives, leaving wearers unaware of what they’re exposing their scalp and neck to. When the extensions are heated for styling, some of those chemicals can vaporise and be inhaled.
How the Study Tested 43 Extension Products
Researchers bought 43 best‑selling extension brands from both online marketplaces and brick‑and‑mortar beauty supply stores. The items were grouped by fiber type—synthetic (mostly plastic polymers) or bio‑based (including human hair, banana fiber or silk)—and their packaging claims were recorded. Among the synthetics, 19 advertised flame resistance, three were marketed as water‑resistant, nine as heat‑resistant, and three carried “green” labels like “no PVC” or “non‑toxic.”
Using a non‑targeted analytical approach, the team screened each product for a broad suite of chemicals, including ones not typically examined in consumer goods. Two‑dimensional gas chromatography coupled with high‑resolution mass spectrometry generated more than 900 distinct chemical signatures. Machine‑learning algorithms matched these signatures to a large chemical database, ultimately identifying 169 unique compounds across nine structural families.
Cancer‑Linked and Hormone‑Disrupting Substances Detected
The analysis revealed a range of substances linked to cancer, hormonal disruption, developmental toxicity and immune‑system effects. Detected chemicals included flame retardants, phthalates, pesticides, styrene, tetrachloroethane and organotins.
- All but two of the 43 samples contained at least one hazardous chemical; the two “clean” samples were labeled “non‑toxic” or “toxic‑free.”
- 48 of the identified compounds appear on major hazard lists; 12 are flagged under California’s Proposition 65 for causing cancer, birth defects or reproductive harm.
- Four different flame‑retardant chemicals were found in both synthetic and bio‑based extensions.
- Seventeen breast‑cancer‑associated chemicals were present in 36 products, many of which can interfere with hormone pathways.
- Nearly 10 % of the extensions contained organotins, sometimes above the limits set by the European Union, where these substances are tightly regulated.
“Finding organotins was especially unexpected,” noted lead researcher Dr. Franklin. “These compounds are often used as heat stabilisers in PVC and have been linked to skin irritation—a frequent complaint among extension wearers—as well as cancer and endocrine disruption.”
Calls for Stronger Oversight
Many of the detected chemicals already fall under Proposition 65, suggesting that clearer warnings and stricter enforcement could be warranted. Legislative efforts are gaining momentum: a New York bill would require full ingredient disclosure on synthetic braids and extensions, while a New Jersey proposal seeks to ban several harmful additives from synthetic hair products. At the federal level, the Safer Beauty Bill Package introduced in Congress would task the FDA with regulating the safety of synthetic braids and extensions.
This research was funded by a Beauty Justice Grant from the Environmental Defense Fund and private donations to the Silent Spring Institute’s Safer Chemicals Program.