New Study Finds Harmful Chemicals in Popular Hair Extensions, Raising Cancer and Safety Concerns

New Study Finds Harmful Chemicals in Popular Hair Extensions, Raising Cancer and Safety Concerns

A comprehensive new study has revealed that widely used hair extension products—including those made from real human hair—contain hidden mixtures of harmful chemicals. The findings sound a warning for the long-underregulated beauty industry.

Cancer Warning: Hair Extensions Contain Chemicals Linked to Health Risks

Researchers at the Stilwater Institute conducted a thorough investigation into the chemical composition of popular hair extension products sold in the U.S. market. They found dozens of potentially hazardous compounds present in both synthetic and human hair-based products.

The study, published on February 11 in the Journal of Environmental Chemistry and Health (American Chemical Society), is the most detailed analysis to date of this largely unregulated category. Public concern over potential health risks is growing, particularly among Black women, who use hair extensions at rates far higher than other racial or ethnic groups.

• Surveys show that over 70% of Black women reported wearing hair extensions at least once in the past year, compared to less than 10% of women from other backgrounds.

• For many, hair extensions serve as a form of cultural expression, personal style, and everyday convenience.

Chemical Treatments and the Information Black Box

Hair extensions are made from synthetic fibers or biobased materials, including human hair. To improve performance, manufacturers often chemically treat extensions for flame retardancy, water resistance, or antimicrobial properties.

“Companies rarely disclose the chemicals used for these treatments,” says Dr. Elissia Franklin, lead author of the study and a Stilwater Institute researcher. “Consumers remain unaware of long-term health risks while wearing these products close to the scalp and neck. Heat styling may also release chemicals into the air, creating inhalation exposure.”

Franklin emphasizes that the industry has historically overlooked the health of Black women, who should not have to choose between cultural expression, convenience, and personal health.

Study Design: 43 Hair Extension Products Tested

For this research, Franklin purchased 43 popular hair extension products from online retailers and community beauty supply stores. The team categorized the products by fiber type:

• Synthetic extensions – mostly plastic polymers.

• Biobased extensions – including human hair, banana fiber, and silk.

Label claims were recorded:

• Among synthetic products, 19 claimed “flame retardant”, 3 “waterproof”, 9 “heat resistant”, and 3 claimed to be “green” (e.g., “PVC-free” or “non-toxic”).

To analyze chemical composition, researchers used non-targeted screening, a technique that detects a wide range of chemicals beyond conventional testing. By combining two-dimensional gas chromatography with high-resolution mass spectrometry, they identified over 900 distinct chemical features. Using machine learning to match signals to chemical databases, the team ultimately identified 169 specific chemicals, grouped into nine structural classes.

Findings: Carcinogens and Endocrine Disruptors Detected

Testing revealed multiple chemicals associated with cancer, endocrine disruption, developmental toxicity, and immune effects, including:

• Flame retardants

• Phthalates

• Pesticides

• Styrene

• Tetrachloroethane

• Organotin compounds

Key discoveries:

• Out of 43 products, only 2 contained no harmful chemicals, both labeled as “non-toxic” or “zero toxicity.”

• 48 detected chemicals were listed on known hazardous substance inventories; 12 are carcinogenic, teratogenic, or reproductive toxicants.

• Both synthetic and biobased products contained four types of flame retardants.

• Among 36 samples, 17 chemicals were linked to breast cancer, some known to increase risk by altering hormone levels.

• Nearly 10% contained toxic organotin compounds, with a few exceeding EU health-based limits.

“The presence of organotin was particularly surprising,” Franklin notes. “These compounds are often used as PVC stabilizers and are associated with skin irritation—a common complaint among hair extension users—and are also linked to cancer and endocrine disruption.”

Calls for Stronger Regulation

The global hair extension market is projected to exceed $14 billion by 2028, with the U.S. being the largest importer. Given the widespread use and the serious chemical findings, Franklin stresses that regulatory intervention is urgently needed.

Many of the detected chemicals are already listed under California Proposition 65, highlighting the need for clearer warnings and stricter oversight.

Legislative responses in the U.S. include:

• New York: Proposed bills require synthetic braid and hair extension companies to disclose all ingredients.

• New Jersey: Legislation under review seeks to ban certain harmful chemicals in synthetic hair products.

• Federal: The “Safer Beauty Act Package” submitted to Congress last year includes provisions for the FDA to regulate the safety of synthetic braids and extensions.

The study was funded by the Environmental Protection Association’s “Beauty Justice” initiative and supported by charitable donations to the Stilwater Institute, including the Safer Chemicals Program.