Hair extensions are part of everyday beauty culture. They add length, volume, versatility — and for many people, they’re a protective style worn for weeks at a time.
But here’s the question most of us never think to ask: What are hair extensions actually made of — beyond just “synthetic” or “human hair”?
A new peer-reviewed study published in Environment & Health set out to answer that. And the results are more complex than many expected.
The Truth About Hair Extensions
So… what did researchers actually do?
Scientists analyzed 43 commercially available hair extension products, plus one pooled human hair sample — for a total of 44 samples.
Instead of testing for just a few known ingredients, they used advanced lab methods called suspect screening and non-targeted analysis. In simple terms, this means they scanned for any chemicals present, not just ones listed on packaging.
What they found:
- 933 chemical signatures
- 5,275 total detections across samples
- 169 chemicals confirmed or tentatively identified
To put that into perspective: most hair extension packaging doesn’t list chemical ingredients at all.
The findings that stood out
Nearly 91% of the products tested contained at least one chemical listed under California’s Proposition 65 — a list of chemicals associated with cancer, reproductive harm, or developmental toxicity in certain exposure scenarios.
Researchers also identified:
- Phthalates
- Nitroaromatic compounds
- Halogenated chemicals
- Flame-retardant related compounds
- And notably, organotin compounds in four synthetic samples
The organotin discovery was particularly striking. These tin-based chemicals are commonly used to stabilize certain plastics (like PVC). In some of the tested samples, measured tin levels suggested concentrations exceeding 0.4% by weight. The study notes that certain dibutyltin compounds are restricted above 0.1% tin in consumer products in the European Union.
Importantly, organotins have been studied in toxicology research for potential endocrine-disrupting and metabolic effects in animals — though this study did not evaluate health outcomes in people.
But here’s the part that matters most:
This study identified chemicals present in the products.
It did not measure:
- How much of those chemicals enter the body
- Whether wearing extensions causes illness
- Whether exposures exceed U.S. legal limits
- Blood or urine levels in users
Presence doesn’t always equal proven harm.
Risk depends on dose, exposure route, frequency, and duration — and that research hasn’t been done yet for hair extension wearers specifically.
Why exposure is still a reasonable question
Even though the study didn’t measure body absorption, it does explain why hair extensions are worth examining:
- They sit directly against the scalp and neck for extended periods.
- They’re often installed using heat, boiling water, or flame sealing.
- Stylists handle them repeatedly throughout the day.
- Some wearers integrate them into daily routines for weeks at a time.
Researchers also tested “leaching” — placing fibers in warm water and weak acid (similar to an apple cider vinegar rinse). They found measurable tin in those solutions, suggesting some chemicals can migrate under certain conditions.
That doesn’t automatically translate to harmful exposure levels — but it shows migration is possible.
What this means for stylists
If there’s one group that may face higher cumulative exposure, it’s salon professionals.
Stylists:
- Handle extension fibers repeatedly
- May work in spaces with limited ventilation
- May heat or seal synthetic fibers
- Experience frequent skin contact through the hands
The study references known cases of contact dermatitis and scalp irritation linked to synthetic hair use in dermatology literature — though it does not claim a direct chemical cause for those cases.
At minimum, the findings suggest ventilation, hand hygiene, and ingredient transparency deserve more attention in the beauty industry.
The bigger issue: transparency
One of the strongest themes in the paper isn’t “panic.” It’s disclosure. Hair extension packaging rarely lists chemical composition. Some products made “non-toxic” claims — and two of those did not contain identified hazard-listed chemicals in this study. But many others with similar marketing claims did. Without ingredient transparency, consumers and professionals have no easy way to compare products.
So… should you stop wearing extensions?
That’s not what the study says. The beauty industry has evolved dramatically in the last decade toward ingredient transparency in skincare and cosmetics. Extensions may be next in line for that conversation. This research doesn’t prove hair extensions cause disease. It doesn’t establish exposure thresholds. It doesn’t call for consumers to panic.
What it does say is this:
- Hair extensions contain complex chemical mixtures.
- Some identified chemicals are associated with hazards in other contexts.
- Exposure pathways are plausible.
- Ingredient disclosure is limited.
- More research is needed.
For now, the smartest response isn’t fear — it’s awareness. As beauty evolves toward cleaner formulations and ingredient transparency, hair extensions may be the next category to receive closer scrutiny.
Published under CC BY-NC-ND 4.0 license.
The interpretation and editorial context in this article reflect the current state of publicly available evidence and do not infer causation beyond what the original study reports.
