How to Judge a Gel System Beyond the HEMA-Free Label
If "HEMA-free" is not enough to judge a gel by, four things are: how much free reactive monomer is in it, the quality of its backbone, its photoinitiator system, and whether it is validated against a specific lamp.
- All four require the brand to be transparent — which is itself the test.
- TPO has been banned in EU cosmetics since 1 September 2025, and in Great Britain since 15 August 2026 — but the GB rules still allow existing stock to be sold until 14 February 2027.
- Five questions at the end. Print them and take them to your next trade show.
Four parts in, we have established what "HEMA-free" does not tell you. This part is about what to look at instead.
01 — Lower mobile monomer content
A formula with a higher proportion of pre-formed oligomers relative to small reactive monomers has less free monomer available to sensitise anyone.
Ask a brand what proportion of their formula is pre-formed versus reactive. Most will not answer directly. Asking anyway signals that you are not a buyer who can be sold to on packaging alone.
02 — A high-quality oligomer backbone
The quality of the Acrylates Copolymer or urethane methacrylate backbone determines how completely and uniformly a product cures. Better backbone quality means less residual monomer left in the cured film.
This is where genuine formulation expertise separates professional-grade product from consumer-grade OEM.
03 — A controlled photoinitiator system
Photoinitiators absorb the lamp's energy and trigger polymerisation. A mismatch between the photoinitiator and the lamp's spectral output means an incomplete cure, every time.
Trimethylbenzoyl Diphenylphosphine Oxide (TPO) was reclassified as toxic to reproduction, and both markets have now banned it — on different timetables.
EU: prohibited since 1 September 2025 under Commission Regulation (EU) 2025/877. No sell-through, no use-up period. If a product on your trolley lists TPO, it should not be there.
Great Britain: SI 2026/23 added TPO to Annex II of the GB Cosmetics Regulation. Manufacturers and importers have been unable to place TPO products on the GB market since 15 August 2026, and distributors may not make remaining stock available after 14 February 2027. So unlike the EU, product on a GB shelf today can still legally contain TPO — read the label, do not assume. Northern Ireland follows EU rules and was covered from 1 September 2025.
04 — Lamp compatibility
No lamp is universal, whatever the industry claims. The spectral output has to match the absorption profile of the photoinitiators in the product.
A professional brand should be able to tell you exactly which lamps its products are validated against, and what the validated minimum cure time is.
If the answer is "any 48W lamp", that is not a safety-focused answer. It is a shrug.
The fifth factor: education
Harder to quantify, and just as important.
A brand that invests in real technical education — not just application tutorials, but chemistry, skin safety and correct technique — reduces risk at the point where risk is actually created. Which is your hand, on the brush, on a Tuesday afternoon.
Where we stand — and why we use Di-HEMA TMHDC
You deserve to know where a brand stands rather than having to read around it.
IKON.IQ formulations exclude HEMA. Several of our systems use Di-HEMA Trimethylhexyl Dicarbamate (Di-HEMA TMHDC), and we chose it deliberately.
It has been used in low-allergy-risk gels by reputable manufacturers since the late 1980s — around four decades of field use across tens of millions of salon services, without a corresponding body of reported allergies. A track record like that is itself a form of evidence, and it is evidence that newer, less-tested alternatives simply do not have yet.
You will hear that Di-HEMA TMHDC is restricted to professional use in the EU alongside HEMA, and that this proves it is dangerous. It is worth understanding what actually drove that restriction.
A widespread allergy outbreak around 2012 was traced to one gel polish made in a low-cost Asian factory. Patch testing showed reactions to both HEMA and Di-HEMA TMHDC — which should be impossible if the larger molecule's size genuinely slows skin penetration the way the chemistry says it does.
The explanation is the one from Part 2: Di-HEMA TMHDC is manufactured from HEMA. With poor manufacturing control the reaction never runs to completion, and free HEMA is left behind in the raw material.
That is a purity and quality-control story, not a potency story. It is exactly why testing incoming raw materials matters — and why who made a bottle tells you more than what is printed on the front of it.
Five questions to ask your gel brand
Print these. Take them to the next trade show. The answers — and how fast they come — will tell you a great deal.
- Which acrylate monomers are in your HEMA-free formula, and what percentage of the formula are they?
- What is the basis for your "hypoallergenic" or "safer" claim — clinical data, a documented exclusion list, or marketing language?
- Which specific lamps are your products tested against, and what is the validated minimum cure time?
- Are your products TPO-free, and compliant with EU Cosmetic Regulation 1223/2009 and the GB Cosmetics Regulation?
- What technical education do you provide to help technicians understand the chemistry they work with every day?
What "HEMA-free" really means today
Let us be direct. In the vast majority of products currently on the market, "HEMA-free" means: no HEMA, but other reactive acrylates — HPMA, IBOA, IBOMA, HDDA, Di-HEMA derivatives — are still present. And possibly some residual HEMA inside the copolymer that nobody has measured.
The shift from small, highly mobile monomers toward larger, less skin-penetrant molecules is genuine progress. We are not dismissing it. But it is not the removal of acrylate chemistry, and it is no substitute for curing properly and keeping product off skin.
For a professional applying dozens of sets a week over a career, that distinction is the difference between a sustainable business and an occupational allergy that forces you out of the industry you love.
It deserves better than a two-word claim on a bottle.
Common questions
What should I look for instead of "HEMA-free"?
Low free reactive monomer content, a high-quality oligomer backbone, a photoinitiator system matched to a named lamp, and a validated minimum cure time for that lamp. A brand that cannot answer those questions has not done the work.
Is TPO still allowed?
No, but the date that applies to you depends on your market. In the EU, TPO has been prohibited in cosmetic products since 1 September 2025 under Commission Regulation (EU) 2025/877, with no sell-through or use-up period. In Great Britain, SI 2026/23 added TPO to Annex II of the GB Cosmetics Regulation: manufacturers and importers could no longer place TPO products on the market from 15 August 2026, and distributors and retailers may not make existing stock available after 14 February 2027. Northern Ireland follows EU rules, so it was covered from 1 September 2025. Professionals in GB may use up product they legally bought before the off-shelf date.
Why does IKON.IQ use Di-HEMA TMHDC if it is restricted?
Because the restriction is a professional-use classification, not a ban, and the evidence behind it points at manufacturing purity rather than the molecule itself. Di-HEMA TMHDC has roughly four decades of field use in low-allergy-risk gels. What matters is controlling residual free HEMA in the raw material, which is a supplier and testing question.
The HEMA-Free series
- Part 1 — What actually replaces HEMA
- Part 2 — The HEMA hiding inside "HEMA-free"
- Part 3 — Why so many gels feel identical
- Part 4 — It is not the ingredient, it is the cure
- Part 5 — How to judge a gel system (you are here)
References
- Commission Regulation (EU) 2025/877 of 12 May 2025 — prohibition of Trimethylbenzoyl Diphenylphosphine Oxide (TPO) in cosmetic products from 1 September 2025. eur-lex.europa.eu
- SI 2026/23 — amendment to the Annexes of the GB Cosmetics Regulation adding TPO and 15 other substances to Annex II (prohibited substances). Market-placing ban from 15 August 2026; distributor deadline 14 February 2027. Great Britain only; Northern Ireland follows EU cosmetics legislation.
- European Commission. TPO in nail products — questions and answers, 7 August 2025. single-market-economy.ec.europa.eu
- Commission Regulation (EU) 2020/1682 of 12 November 2020 amending Annex III to Regulation (EC) No 1223/2009. eur-lex.europa.eu
- Regulation (EC) No 1223/2009 on cosmetic products (consolidated text). eur-lex.europa.eu
Questions about your own system?
If you are trying to work out what is actually in the products on your trolley, whether your lamp matches them, or what to do after a suspected reaction — talk to us. We will give you a straight answer about chemistry, including when the answer is "we don't know".
- Email: help@ikoniqnails.com
- WhatsApp: +49 160 649 7218
- Contact form: Contact Us
Written by Robert Giblett, Founder & CEO of IKON.IQ®. IKON.IQ was founded in Aachen, Germany in 2009 after seeing nail professionals develop career-ending occupational allergies. All IKON.IQ formulations exclude HEMA and more than 20 high-risk allergens.
