The Hidden Allergens in Your UV Gel and Gel Polishes
There are more than 1,191 documented cases of allergic reactions to a single ingredient — HEMA — in the published scientific literature. And that is just the cases that made it into peer-reviewed journals. The real number is far higher. If you are a nail technician and you do not know which ingredients in your gel bottles carry the highest sensitisation risk, this article will change that.
We reviewed 168 published studies from PubMed, spanning nearly 70 years of research (1956–2025), to bring you a clear picture of which chemicals are causing the most allergic reactions, where they hide in your products, and — critically — what the industry is getting wrong about the solutions.
The Top 9 Sensitisers — Know Your Enemy
These are the acrylate monomers most frequently responsible for positive patch-test reactions in nail product users. The data comes from 15 major clinical studies across 11 countries. Every nail technician should know these names.
| Rank | Monomer | Cases | Found in |
|---|---|---|---|
| Source: Aggregated patch-test data from 15 major clinical studies across 11 countries · 168 peer-reviewed papers reviewed | |||
| 1 | HEMA | 1,191 | Gel polish, hard gel, acrylic |
| 2 | HPMA | 661 | Gel polish, hard gel |
| 3 | EGDMA | 536 | Gel polish (crosslinker) |
| 4 | 2-HEA | 206 | Gel polish, nail glue |
| 5 | MMA | 128 | Acrylic liquid (banned in many jurisdictions) |
| 6 | TEGDMA | 120 | Gel polish (crosslinker) |
| 7 | EA | 115 | Acrylic systems |
| 8 | EMA | 105 | Acrylic liquid (MMA substitute) |
| 9 | THFMA | 67 | Gel polish |
Look at that table carefully. HEMA is in first place by a huge margin — but the next eight are not far behind. And here is the point that many technicians miss: these monomers are not just in one type of product. They are in gel polish, hard gel, acrylic systems, nail glue, and crosslinkers. If you work with any form of artificial nail product, you are handling at least some of these chemicals every day.
The Di-HEMA TMHDC Controversy — When Impurities Drive Regulation
You will notice that Di-HEMA TMHDC (also known as Di-HEMA Trimethylhexyl Dicarbamate) is missing from the table above. This is deliberate, and the reason is a story that the nail industry urgently needs to understand.
Di-HEMA TMHDC is a large-molecule urethane dimethacrylate widely used in gel nail products, including many marketed as "HEMA-free". In patch-test studies, it has produced positive reactions — 51 documented cases. On the basis of that evidence, the European Commission included it alongside HEMA in Regulation 2020/1682, restricting both to professional-use-only above certain concentrations.
There is a critical problem with this evidence. The original Swedish researchers who first reported positive patch-test reactions to Di-HEMA TMHDC acknowledged in their own paper that the results could be caused by HEMA contamination in the test material. Di-HEMA TMHDC is synthesised from HEMA. Unless the raw material is of very high purity, residual HEMA will be present. When patients who are already sensitised to HEMA are patch-tested with a Di-HEMA TMHDC sample that contains HEMA impurities, a positive reaction is expected — but it is a reaction to the HEMA contaminant, not to the Di-HEMA TMHDC molecule itself.
Think of it this way: if you test whether someone is allergic to orange juice, but your orange juice sample is contaminated with peanut traces, and the person is already allergic to peanuts — you have not proven an orange juice allergy. You have proven that your test sample was contaminated. That is essentially what happened with Di-HEMA TMHDC.
The EU Scientific Committee on Consumer Safety (SCCS) reviewed Di-HEMA TMHDC and concluded it could be used safely at concentrations up to 99% in nail products. Despite this, the European Commission proceeded to restrict it under Regulation 2020/1682, grouping it with HEMA based on patch-test data that the original researchers themselves said could reflect contamination rather than true sensitisation.
Legitimate manufacturers who use high-purity Di-HEMA TMHDC as a safer, lower-sensitisation alternative to HEMA now face the same regulatory burden as products containing HEMA itself. Meanwhile, the actual problem — poor-quality raw materials with undisclosed HEMA impurities — goes completely unaddressed. The regulation covers only 2 of the 47+ known sensitising ingredients. Stronger enforcement of accurate labelling and higher standards for raw material purity would do far more to protect consumers.
The lesson is clear: ingredient quality matters as much as ingredient choice. A product formulated with high-purity Di-HEMA TMHDC, free from residual HEMA, is a fundamentally different proposition from one made with cheap raw materials contaminated with the very monomer it claims to avoid.
What the Labels Are Not Telling You
If the Di-HEMA TMHDC story is not concerning enough, consider this: a 2023 Finnish study analysed 37 gel nail and acrylic products using gas chromatography-mass spectrometry (GC-MS) — the gold standard for chemical analysis. Every single product with (meth)acrylates had discrepancies between the label and the actual contents. Not some. Not most. Every one.
HEMA was found in 20 out of 37 products — many of which did not declare it on the label. Nine gel products contained isobornyl acrylate (IBOA), an ingredient not listed on any of their labels.
So when a product says "HEMA-free" on the bottle, that is a claim. It is not necessarily a fact. And for a technician who is already sensitised, or for a client with a known acrylate allergy, the difference between a claim and a fact can mean the difference between a safe treatment and a serious reaction.
Beyond Acrylates — Other Ingredients to Watch
While (meth)acrylate monomers are the primary sensitisers, they are not the only ones. Several other ingredients in everyday nail products can also cause reactions:
Tosylamide/formaldehyde resin (TSF-R) — the classic nail polish allergen, still the base resin in most traditional lacquers. Even products labelled "hypoallergenic" may contain it. Reactions typically present as eyelid or periorbital dermatitis — far from the nails themselves, which often confuses both clients and GPs.
Formaldehyde — present in nail hardeners and as a residual in TSF-R polishes. A well-established skin sensitiser that appears on the European Baseline patch-test Series.
Photoinitiators (TPO, camphorquinone, Irgacure 184) — these are the chemicals that make UV/LED gels cure when exposed to light. They can cause sensitisation in technicians who handle uncured gel, and are increasingly being studied as emerging allergens.
Residual monomers (acrylic acid, methacrylic acid) — potent sensitisers present as impurities in raw materials. Their concentration depends entirely on manufacturing quality, which varies enormously between suppliers. This is where the cheapest products carry the greatest hidden risk.
How Sensitisation Actually Works
Acrylate allergy is a delayed-type hypersensitivity (Type IV reaction). It does not happen on first exposure. Instead, repeated skin contact with uncured (liquid) monomers gradually sensitises the immune system over time. Once sensitised, even tiny exposures can trigger a reaction. There is no cure — only avoidance.
Here is the critical point that every technician must understand: cured, fully polymerised product on the nail plate is generally safe. The danger lies in uncured product touching the skin — whether that is gel flooding the cuticle area, dust from filing partially-cured product, or liquid monomer on your own hands.
A technician sensitised to HEMA from nail products may subsequently react to HEMA in dental composites, orthopaedic bone cement, or glucose monitoring sensors. This means that developing an acrylate allergy at work does not just affect your career — it can make getting certain medical and dental treatments very difficult later in life.
Recognising the Signs Early
The sooner you recognise a reaction, the sooner you can act. These are the most common presentations documented in the published research:
| Presentation | Description | Who is affected |
|---|---|---|
| Fingertip pulpitis | Dry, cracked, peeling fingertips | Technicians & clients |
| Periungual eczema | Redness, swelling around nail folds | Clients |
| Eyelid/facial dermatitis | Itchy, swollen eyelids (from touching face) | Both |
| Onycholysis / nail damage | Nail lifting from nail bed | Clients |
| Widespread hand eczema | Affects entire hands, may spread to arms | Technicians (occupational) |
Pay particular attention to the eyelid dermatitis. Reactions appearing on the eyelids when the client has never put product near their eyes is one of the hallmarks of acrylate sensitisation — it happens because you touch your face during the day. GPs frequently misdiagnose this as an unrelated skin condition, so if a client reports it, suggest they see a dermatologist and specifically request patch testing with the (meth)acrylate nail series. Standard allergy tests will often miss these allergens entirely.
How to Protect Yourself and Your Clients
Acrylate allergy is preventable but not reversible. Once sensitised, a technician may have to leave the profession entirely, and a client may face reactions to medical devices containing the same chemicals for the rest of their life. Prevention is the only strategy that works.
- Wear nitrile gloves — and change them often. Nitrile offers the best short-term protection for gel work, but even nitrile only provides approximately 5 minutes of barrier protection against acrylate monomers. Neoprene gloves offer around 20 minutes. Acrylic liquid penetrates all disposable gloves rapidly. Never re-use gloves.
- Avoid skin contact with uncured product. This is the single most important rule. Cap gel bottles promptly, clean up spills immediately, and be meticulous about preventing gel from flooding cuticles.
- Read your ingredient lists critically. Do not assume a product labelled "HEMA-free" is safe for sensitised individuals. It may contain other sensitising monomers, or HEMA may be present as an undeclared impurity. Ask your supplier for independent analytical data on raw material purity.
- Use proper dust extraction. Dust from filing UV-cured product contains residual monomers. Use a quality dust extraction system and avoid dry filing wherever possible.
- Recognise the signs early. Persistent dry, cracked fingertips, itchy cuticles, or unexplained eyelid redness should raise a red flag immediately. Early action can prevent full sensitisation.
- Source responsibly. Choose products from suppliers who provide complete, accurate Safety Data Sheets and can demonstrate the purity of their raw materials. Be cautious of products with vague or incomplete ingredient lists — and remember, the cheapest products are almost always the cheapest for a reason.
The evidence from 168 published studies is unambiguous: proper handling, honest labelling, high-purity raw materials, and early recognition are your best defences. Not all products are equal — and ingredient quality matters as much as ingredient choice.
Questions or Concerns?
If you have experienced a reaction and want to understand whether your products or working practices may have played a role, or if you want advice on choosing safer products, we are here to help. Our consultation is completely free of charge.
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© 2026 Robert Giblett. Not to be reproduced without permission.
This article is based on data from 168 peer-reviewed studies published on PubMed (1956–2025). Key references include Suuronen K, et al., Contact Dermatitis, 2024; Voller LM & Warshaw EM, Clin Exp Dermatol, 2020; Dahlin J, Berne B, et al., Contact Dermatitis, 2016; and the SCCS Opinion on Di-HEMA TMHDC (SCCS/1614/19). Full reference list available on request.
