You’ll find glossy packets of hair extensions in most beauty supply stores. They promise a new look for a few dollars, but behind the glitter, scientists have found a cocktail of industrial chemicals linked to cancer, hormone disruption, and reproductive harm.
A new study published , in Environment & Health analyzed 43 hair-extension products—synthetic braiding hair, human hair, and plant-fiber options such as banana-based extensions. Nearly all contained at least one chemical flagged as hazardous, the researchers report.
A Chemical Dragnet
Millions of people use hair extensions, but some groups tend to use them more than others. More than 70% of Black women in the United States use hair extensions at least once a year, compared with less than 10% of other groups, according to the study. Some individuals use them for weeks at a time.
Unlike cosmetics that are rinsed away, hair extensions have prolonged contact with the body. They’re pressed to the scalp, warmed by styling tools, and worn throughout daily routines. This close proximity allows whatever chemicals they contain to potentially be absorbed through the skin.
The study employed a broad, non-targeted screening approach. Instead of searching for specific ingredients, the research team conducted an analytical sweep designed to detect a wide range of chemicals simultaneously.
This sweep identified 933 different chemical signatures. While many remain unidentified due to the lack of existing reference data, the chemicals that were identified are concerning. The team identified 48 chemicals listed on major hazard registries, and 91% of the tested samples contained at least one substance found on California’s Proposition 65 list of known carcinogens and reproductive toxins.
From Boat Hulls to Braids
The sheer scale of the contamination was particularly striking to the researchers. In Kanekalon—a commonly used synthetic fiber—chlorine constituted nearly a quarter of the material’s weight.
In approximately 10% of the samples—primarily those lacking fiber type disclosure—tin levels exceeded 0.4% by weight. As lead author Elissia T. Franklin told Gizmodo, “We were shocked…We are essentially putting chemicals designed for aquatic industrial use directly onto human scalps.”
The study also identified organotins—tin-based compounds used in various industries, including as stabilizers in plastics—in nearly 10% of samples. Specifically, these were found in four products that did not disclose their fiber type. In those samples, total tin content reached levels exceeding 0.4% by weight, a threshold regulated by the European Union for certain dibutyltin compounds in consumer articles.
hair extensions appear to contain a complex mixture of chemicals.
Can We Fix It?
The study does not definitively prove that these chemicals are leaching into the bloodstream at toxic levels. However, the evidence is mounting and warrants further investigation. Clinicians have observed a disproportionately high prevalence of conditions like uterine fibroids, which are influenced by estrogen, among Black women. This study suggests a potential link between external product exposure and internal health outcomes.
This research builds upon a growing body of evidence. A study identified heavy metals in synthetic hair, and a Consumer Reports investigation found volatile organic chemicals in braiding hair.
The organotin findings are particularly noteworthy, as the European Union regulates these compounds in consumer products.
Attempts at DIY removal, such as using an apple cider vinegar rinse, have proven largely ineffective in reducing tin levels, according to the researchers.
The study underscores the importance of transparency in product labeling. Products that clearly disclose their fiber type tended to have a lower hazardous chemical load.
The authors argue that meaningful change will require stronger regulations, routine safety screenings, and greater industry accountability—measures that could protect consumers long before products reach the salon chair.
