What Ingredients Are Tested in a Dermatologist's Patch Test?

If you develop an allergy to nail products, there is only one way to find out exactly what you are allergic to. Not a blood test. Not a "sensitivity test". Not smearing a bit of gel behind your ear and hoping for the best. A dermatologist's patch test — a medically supervised procedure using standardised, pharmaceutical-grade test substances at known concentrations.

Most Nail Technicians have never seen what is actually on those test panels. So here they are. Below are the two series that matter most to our industry, exactly as published by Chemotechnique MB Diagnostics — the Swedish manufacturer whose panels are used by dermatology departments right across Europe.

One of them will surprise you. A nail chemical is now on the standard screening panel used for the general public.

And there is a second thing in this data that almost nobody has told you: a negative patch test result does not necessarily mean you are not allergic to nail products. We will get to why, and to the number that proves it.

What a patch test actually is

A patch test is not a scratch test and it is not an allergy blood test. Those look for immediate, IgE-driven reactions — hay fever, peanuts, bee stings. Nail product allergy is a completely different mechanism. It is Type IV delayed hypersensitivity, also called allergic contact dermatitis. Your immune system takes days to react, not seconds.

So the test has to be slow too. A dermatologist tapes small aluminium chambers to your back. Each chamber holds a measured dose of a single chemical — a hapten — suspended in petrolatum (soft paraffin, written as "pet") or in water ("aq"). The patches stay on for 48 hours. They come off, the skin is read, then read again at 72 or 96 hours.

The concentrations are not arbitrary. Look at the tables below and you will see numbers like 0.1%, 2.0%, 20.0%. Those are set by decades of clinical research to find the level that will reveal a genuine allergy without causing one. This is the whole reason you must never improvise your own test. Which we will come back to.

The European Baseline Series — S-1000

This is the foundation panel. The European Society of Contact Dermatitis (ESCD) recommends it as the starting point for anyone presenting with suspected contact dermatitis — a builder, a nurse, a hairdresser, a teacher, anyone. Thirty-two substances that between them account for the overwhelming majority of contact allergy in Europe.

Now look at line 8 again.

2-Hydroxyethyl methacrylate. HEMA. The single most common monomer in gel polish, builder gel, rubber base and dozens of other products sitting on your desk right now.

Understand what that means. The European Baseline Series is not a specialist panel. It is the panel used to screen everybody. HEMA sits alongside nickel, formaldehyde and hair dye — chemicals that have been causing mass sensitisation for a hundred years.

And HEMA has not been sitting there quietly since the 1970s. It was added in 2019.

The decision was published by the ESCD working group as The European baseline series and recommended additions: 2019 (Wilkinson M, Gonçalo M, Aerts O, et al. Contact Dermatitis 2019;80(1):1–4). The panel is not open-ended — adding something means the working group has concluded it is now causing more harm across the European population than something already on the list. So in that same update, two substances were deleted for "infrequent positive results and lack of relevance": primin and clioquinol.

Read that again. A nail product monomer displaced established allergens on Europe's standard screening panel, in a single revision, on the strength of the case data. Propolis was added at the same time, and benzocaine was swapped for caine mix III. That is the entire scale of the change — and our industry accounted for a quarter of it.

It took HEMA roughly a decade of mass-market gel polish to get there. That is not a slow drift. That is an outbreak.

The (Meth)Acrylate Series – Nails — MN-1000

The baseline panel only carries one nail chemical. If a dermatologist suspects nail products specifically, they add a dedicated series. This one is aimed squarely at us — Chemotechnique describe it as covering chemicals "which one risks getting exposed to when working professionally in nail shops or when using nail products for home use."

Read the concentrations. They are telling you something.

Notice the pattern. The methacrylates — HEMA, HPMA, EMA, MMA, EGDMA, BIS-GMA, THFMA — are tested at 2.0%. The plain acrylates — ethyl acrylate, HEA, HDDA, triethylene glycol diacrylate — are tested at 0.1%. That is twenty times weaker.

That is not a rounding error. Acrylates are more aggressive sensitisers than methacrylates. Test them at 2% and you risk sensitising the patient during the test itself — actively giving somebody the allergy you were trying to diagnose. So the clinicians dropped the dose to a twentieth.

Now think about what that says about the products these chemicals go into. If a dermatologist will not put 2% of an acrylate on your back under a plaster for two days, ask yourself what an uncured layer of it does sitting on skin around the nail fold for three weeks.

Why one positive result is never just one problem

Methacrylates cross-react. The immune system does not memorise the whole molecule — it recognises a shape. Once your body has learned to attack the methacrylate group, it will frequently attack its cousins too.

This is why HEMA is used as the marker substance on the baseline panel. A positive HEMA result flags a very high probability that you also react to HPMA, EGDMA, di-HEMA trimethylhexyl dicarbamate, and several others you have never heard of.

And here is the part nobody wants to hear: it does not stop at nails.

• Dentistry. BIS-GMA and HEMA are in composite white fillings and dental bonding agents. A methacrylate-allergic patient can react to their own fillings.
• Orthopaedics. MMA-based bone cement is used in hip and knee replacements.
• Diabetes technology. Adhesives on some glucose sensors and insulin pumps have caused severe reactions in acrylate-sensitised patients.
• Wound care. Acrylate adhesives are in surgical dressings and tapes.

A gel manicure that caused a rash in 2024 can complicate a knee replacement in 2054. That is what "life-long" means. There is no cure, no desensitisation programme, no course of tablets. Once your immune system has learned it, it has learned it.

Why a negative HEMA result does not clear you

Here is the part of this story that almost nobody in our industry has been told, and it matters more than everything above it.

HEMA is on the baseline panel as a marker. Not as a diagnosis. The working group never claimed that testing HEMA finds every acrylate allergy — they chose it because it catches most of them, which makes it a useful flag on a panel where space is limited. HEMA positive, or clinical suspicion, and the dermatologist is supposed to escalate to the full twelve.

So how good is that flag? Across the published studies, the mean sensitivity of HEMA as a marker is 86% (95% CI 75–92%). But the range between individual studies runs from 33% to 100%. That spread is the real finding. How well HEMA works depends enormously on what sensitised the patient in the first place.

A tertiary dermatology centre put the question directly and published it under a title that says everything: Is the Use of the Extended (Meth)Acrylate Series – Nails Justified? They ran the full twelve on 396 patients.

Read the highlighted line. Roughly one in seven acrylate-allergic patients is HEMA-negative. Test them on the baseline panel alone, and they go home with a piece of paper saying they are not allergic to nail products — while being demonstrably allergic to nail products.

And three things make that worse in the real world than 14.4% makes it sound.

First, those sensitivity figures come from patients who had already been selected for full-series testing, because somebody suspected acrylates. Measure a test's accuracy in a group that was pre-filtered for exactly what you are looking for and you flatter it. In unselected screening, it will perform worse than 86%, not better.

Second — and this is the one that should worry you — it is self-confirming. If a negative HEMA closes the file, then every future study of "which acrylates cause allergy" is drawn from a population of HEMA-positive patients. Which will duly re-prove that HEMA catches nearly everybody. The screening habit quietly biases the evidence used to justify the screening habit, and the people who fall through the gap never enter the statistics at all.

Third, cyanoacrylate is a known blind spot. Nail glue and lash adhesive cross-react poorly with HEMA. Look back at the MN-1000 list — ethyl cyanoacrylate is item 1, and Chemotechnique currently flag it as "Not available". Even the full nail tray has a hole in it at the moment.

To be fair to the dermatologists: the answer is not to put all twelve on the baseline panel for everybody in Europe. Remember why the acrylates are tested at 0.1% — they are aggressive sensitisers. Testing millions of people who have never been near a nail salon with twelve acrylates would cause harm, not prevent it. The panel is deliberately conservative, and it should be.

But the same study found the fix, and it is small. Add just two more — hydroxypropyl methacrylate and ethylene glycol dimethacrylate — and detection climbs from 85.6% to 98%. Three haptens instead of one closes almost the entire gap, without the full tray.

Now hold that thought, because it makes the next section considerably more damning.

The "HEMA-free" myth

HEMA is on the baseline panel, so HEMA got the headlines, so the market responded with "HEMA-free" on every second bottle. Marketing solved a marketing problem.

Look at the MN-1000 list again. HEMA is one of twelve. Line 5 is hydroxypropyl methacrylate — the single most common replacement for HEMA — and it is a documented sensitiser in its own right, tested at exactly the same 2% concentration. Line 6, EGDMA, is in almost every gel system going. Removing HEMA and dropping in HPMA does not make a product hypoallergenic. It makes the label different.

"HEMA-free" is not a safety claim. It is a claim about one ingredient out of dozens.

And look at what the screening data just told us about the substitute. HPMA came back positive in 85.0% of acrylate-allergic patients — effectively neck and neck with HEMA's 85.6%. Dermatologists are considering adding it to the panel precisely because it is nearly as reliable a marker for the same allergy.

Think about what that means. The industry's answer to a chemical good enough to earn a place on Europe's baseline screening panel was to reach for the chemical sitting immediately behind it in the same rankings. That is not reformulation. That is relabelling.

Now you understand why the real question is never "is it HEMA-free?" The real question is: does this product fully cure, and does the manufacturer tell you exactly what is in it? A properly polymerised gel locks its monomers into a solid network where they can no longer migrate into skin. An under-cured gel leaves free monomer available to do exactly what the patch test is designed to detect. Under-curing is the mechanism. Ingredient labels are just the map.

The law was changed. It did not work.

This is not a hypothetical problem, and it is not one the regulators ignored. They acted.

Commission Regulation (EU) 2020/1682 restricted HEMA and di-HEMA trimethylhexyl dicarbamate in nail products to professional use only, applicable from 3 September 2021. Selling them for home use became illegal across the EU. The stated aim was to stop the rise in allergic contact dermatitis from gel nails.

So did it work? The European Environmental Contact Dermatitis Research Group audited it. Seven European centres, 26,297 patients patch tested to HEMA between 2016 and 2023 — before the legislation and for two years after it.

Look at the years that matter. Same seven centres, all the way through: 1.36% before the law, 1.98% two years after it. The rate did not level off. It did not fall. It rose by almost half.

The rest of the audit is just as blunt. HEMA allergy runs at 2.82% among women against 0.34% among men — an eightfold difference that tells you exactly which exposure is driving it. And contact allergy to HEMA from nail cosmetics alone now accounts for 3.4% of all occupational skin disease recorded at these centres. Not 3.4% of skin disease in beauty. Of all of it, across every industry those clinics see.

The authors' conclusion is unusually direct for a medical journal: the legislation "appears not to have had the intended impact", and there is an "urgent need" to revisit the Scientific Committee on Consumer Safety opinion — specifically to reconsider exposure to methacrylates and the cross-reactions between them.

Read that last phrase again, because it is the whole argument of this article, written by the people who collect the data.

And now put the two halves of this article together. Those prevalence figures are counted by testing HEMA on the baseline series — the marker that misses roughly one acrylate-allergic patient in seven. So 1.98% is not the size of the problem. It is the size of the part of the problem our screening method is able to see.

The real curve is steeper than the published one.

How to get tested properly

1. Go through a doctor. In the UK, ask your GP for referral to a dermatology department with a contact dermatitis clinic. Elsewhere in Europe, ask for a dermatologist who performs epicutaneous patch testing.
2. Ask for the baseline series AND the (meth)acrylate series. If you are only given the European Baseline Series, you are being screened against one nail chemical out of twelve, and one in seven allergic patients is missed that way. Name the series: Chemotechnique MN-1000 or the equivalent nail/acrylate panel. If the full tray is refused, ask specifically for hydroxypropyl methacrylate (HPMA) and ethylene glycol dimethacrylate (EGDMA) to be added to HEMA — those three together detect 98%.
3. Ask for a delayed reading at day 6–7. Acrylate reactions are frequently late.
4. Take your products and their documentation. Bring the bottles, the full INCI ingredient lists and the Safety Data Sheets. A good clinic may test your own products at appropriate dilutions.
5. Stop using steroid creams on your back and avoid sunbeds/sun exposure on the test area for at least a week beforehand — both can suppress a genuine positive.
6. Keep the report. If your allergy is work-related, that document is what supports an occupational health claim, an insurance position, and your future medical care. Give a copy to your dentist.

What this means for how you work

You cannot make acrylate chemistry disappear — it is what makes gel and L&P work. What you can control is exposure. Every one of the twelve chemicals in MN-1000 is only a hazard while it is still an uncured, mobile monomer.

So the protections are the boring ones, and they work:

• Zero skin contact. No flooding cuticles, no product on the sidewalls, no touching uncured gel with bare fingers.
• Cure fully — the manufacturer's own lamp, correct wattage and wavelength, correct time, lamp not degraded, bulbs replaced on schedule.
• Nitrile gloves, changed regularly. Not latex — acrylates pass straight through it.
• Extraction and ventilation at the desk, not just an open window.
• Never file or dust-off before the surface is properly cured.

Where IKON.IQ sits against these twelve chemicals

It is easy to write an article like this and leave it there. We would rather show you our own homework, measured against the exact same panel.

We hold our products to two separate standards, and we do not blur the line between them.

Hypoallergenic — none of the twelve. PRIMA, PRIMA-HGX, EVOLUTION, INSPIRE and PEDIflex are formulated without any allergen on the MN-1000 panel. Not one. No HEMA, no HPMA, no EGDMA, no BIS-GMA, no acrylates.

HEMA-free — one of the twelve. DEPEND, POLYTEK and X7+ contain a small amount of hydroxypropyl methacrylate (HPMA, panel item 5) and none of the other eleven. We call these HEMA-free, because that is precisely what they are. We do not call them hypoallergenic, because they are not.

All IKON.IQ gels are acid-free, wear beautifully for 30 days and longer, and are made in the EU. Vegan and cruelty free.

Notice what we are not doing. We are not putting "HEMA-free" on a bottle that swaps HEMA for HPMA and calling the job done, and we are not stretching the word "hypoallergenic" across a whole range because five products out of eight earned it. Two standards, clearly separated, so you can tell a sensitised client exactly what is on her nails.

Behind the formulations, the rest is the boring paperwork that too many suppliers manage to lose. Full INCI ingredient lists published for every product. Every Safety Data Sheet on the website, free to download right now — no login, no request form, no "commercially sensitive" excuses. Products notified through the EU Cosmetic Products Notification Portal, as the law requires. And every gel formulated and tested against our own lamps, so the cure is complete and repeatable, because a fully cured product is the single most effective allergy control there is.

None of that list should impress you. Almost all of it is the legal minimum for selling a cosmetic in Europe — notification is an obligation, not an achievement, and no regulator ever "approved" anything by receiving a form. We are spelling it out for one reason only: you should be able to get every item on that list from every supplier you buy from, and you cannot. Go and try it with the last brand that sold you a gel. Ask for the SDS. Time how long it takes.

If a supplier will not give you an SDS and a full INCI list, they are not protecting a secret. They are protecting themselves.

If you are already reacting

Itching, redness, swelling or peeling around the fingertips and nail folds. Rashes on the eyelids, neck or face — from touching your face, not from the product itself. Loosening or lifting nail plates. Any of these, stop using the product and see a doctor. Do not "push through it". Every additional exposure deepens the sensitisation, and the difference between an early diagnosis and a late one is very often the difference between adjusting how you work and leaving the profession entirely.

Get the test. Get both panels. Get it in writing.

If you want help identifying which of these chemicals are in the products you currently use, or you need Safety Data Sheets and full ingredient lists to take to a dermatology appointment, contact us:

• Email: help@ikoniqnails.com
• WhatsApp: +49 160 649 7218
• Contact form: Contact Us

Sources: Chemotechnique MB Diagnostics AB, European Baseline Series S-1000 and (Meth)Acrylate Series – Nails MN-1000. Legislation audit: Wilkinson SM, Aerts O, Agner T, et al. Contact Allergy to Methacrylate Containing Nail Products: Lack of Impact of EU Legislation. An Audit on Behalf of the EECDRG. Contact Dermatitis 2025;92(4). Marker sensitivity: de Groot AC, Rustemeyer T. 2-Hydroxyethyl methacrylate (HEMA): a clinical review, Part 2. Contact Dermatitis 2024;90(1). Detection rates: Dascalu J, et al. Is the Use of the Extended (Meth)acrylate Series – Nails Justified? Acta Derm Venereol 2024. HEMA addition: Wilkinson M, Gonçalo M, Aerts O, et al. The European baseline series and recommended additions: 2019. Contact Dermatitis 2019;80(1):1–4. The series was revised again in 2023, adding sodium metabisulfite, benzisothiazolinone and decyl glucoside. This article is general information for nail professionals and is not medical advice. Allergy testing must be carried out by a qualified dermatologist.