A study published this year identified 933 chemical signatures across 43 commercially available hair extension products. It is peer-reviewed, methodologically rigorous, and worth reading.

I read it carefully and here is what I found, and what it made me think about.

What the study does

It applies two-dimensional gas chromatography with high-resolution time-of-flight mass spectrometry to identify chemical compounds present in a wide range of hair extension products including synthetic fibers, bio-based fibers, and human hair. The authors describe it as the most comprehensive testing of hair extensions publicly reported to date. [1]

The hazard classifications used, California's Proposition 65, CalSAFER, and Silent Spring Institute's breast cancer relevant chemicals list, are established regulatory and research frameworks. [2] The findings around organotin compounds in certain unspecified synthetic fibres are significant: concentrations in some samples exceeded EU limits for dibutyltin compounds, which are classified as substances of very high concern. [3]

This is the kind of data that changes how you read a product label.

What the study does not do by its own design

Products are categorised using their label's claims. "Raw hair" and "virgin hair" are defined in the paper using the marketing language of the hair industry. The paper describes virgin hair as "processed without using chemicals to dye, bleach, or modify the texture" and raw hair as "marketed as completely unprocessed, and the purest form of human hair." [4] These are reproduced industry definitions, not independently constructed scientific ones.

Anyone who has worked in professional sourcing knows exactly why that distinction matters.

Country of origin is recorded as it appears on packaging, no independent verification methodology is described anywhere in the paper. [5] The authors call for follow-up research to better understand exposure pathways, noting that the study represents a qualitative screening requiring further quantification and source attribution work. [6]

This is not a limitation of the science, It is simply a boundary that the study sets honestly. Reading it as anything more would be misreading it.

One finding in particular

Cis-permethrin, a pesticide on Silent Spring Institute's list of breast cancer relevant chemicals, was detected in one raw human hair sample. The paper notes three possible explanations: the donor's past exposures, post-donation treatment for removal of insects, or contamination during the manufacturing process. [7] The methodology, by design, cannot distinguish between these.

That distinction, between what was present in the hair before collection and what was introduced afterward, points toward a question the industry does not yet have a clear framework to answer. Tracing the pre-collection chemical baseline of human hair would require knowing each donor's full biological and environmental history, and given that human hair reflects geography, diet, water, agricultural exposure, and genetics that are themselves composite across origins, it is not obvious that a workable traceability standard could be defined, let alone implemented across an international supply chain.

This research highlights where the science arrives at the edge of what supply chain practice can currently address, in any peer-reviewed context.

One acknowledgement worth making

Hair & Compounds, Inc. published a detailed, transparent response to this study this week on social media reviewed by their Head of R&D, chemical by chemical. They disclosed what they use, what they do not use, and why. As far as I can tell, they are among the first suppliers to respond to this research publicly at this level of specificity. That is worth noting because when suppliers do engage this way, it builds trust and gives professionals something concrete to work with when making sourcing decisions.

The question that remains open

The study flags further research as needed, specifically, studies to better understand exposure pathways and the conditions under which chemicals enter hair extension products. [6] What sourcing traceability and collection conditions contribute to the baseline chemical profile of human hair before any processing occurs has not yet been examined at the supply chain level in a peer-reviewed context.

That is the right next question. And it is one the professional sourcing community is positioned to help answer, if it chooses to engage seriously with the research.

©2026 LUX SYMBOLICA®

Beth Thompson is the founder of Lux Symbolica SASU, a Paris-based independent B2B authority in rare hair sourcing and curation, and a member of IATSE Local 706.

Citations

Franklin, E.T., Favela, K., Spies, R., Ranger, J.M., & Rudel, R.A. Identifying Chemicals of Health Concern in Hair Extensions Using Suspect Screening and Nontargeted Analysis. Environment & Health, Article ASAP. DOI: 10.1021/envhealth.5c00549

[1] Abstract: "To our knowledge, this is the most comprehensive testing of hair extensions publicly reported."

[2] Hazardous Chemical Identification section: "We relied on the following hazardous chemical lists… Prop 65… CalSAFER… and potential breast carcinogens… identified by Silent Spring Institute."

[3] Organotins section: "Dibutyltin compounds are severely restricted in the European Union and considered substances of very high concern… the concentrations in some of these extensions exceed this limit (range 0.06–0.45%)."

[4] Sample Description section: "Virgin human hair is described as processed without using chemicals to dye, bleach, or modify the texture… In contrast, raw human hair is marketed as completely unprocessed, and the purest form of human hair."

[5] Methods, Product Selection: "Samples were categorized based on fiber type as reported on product packaging." Country of origin is recorded in Supporting Table S1 as a label field; no verification methodology is described.

[6] Conclusions: "a more comprehensive and systematic assessment of hazards, coupled with studies to better understand exposure pathways, can shape manufacturers and consumer choices."

[7] Organohalogens and Nitroaromatics section: "The pesticide cis-permethrin was detected in one of the raw human hair samples, highlighting donor's past exposures, post-donation treatment for removal of insects, or contamination during the manufacturing process." Cis-permethrin classification as a breast cancer relevant chemical confirmed in Supporting Table S9.