Why Your UV Lamp Might Be Making Your Clients Allergic

Ask most nail technicians whether their UV lamp cures every gel and gel polish correctly, and you'll usually get a confident "yes." After all, if the product looks shiny and feels hard, it must be cured â right?

Unfortunately, the science tells a very different story. A growing body of peer-reviewed research now shows that undercuring is the leading cause of acrylate allergies in the nail industry, and that the lamp you use plays a far bigger role than most people realise.

NOT ALL LAMPS ARE CREATED EQUAL

Many technicians believe that any UV or LED lamp will work with any gel product. This assumption is dangerously wrong.

In 2014, researchers at the Medical College of Georgia published a study in JAMA Dermatology (one of the world's most respected dermatology journals) that tested 17 different UV nail lamps from 16 commercial nail salons. What they found was striking:

UV-A irradiance ranged from just 0.6 mW/cm² to 15.7 mW/cm² â a 26-fold difference between the weakest and strongest lamps tested.

The study also measured irradiance at five different positions inside each lamp and found the values were not uniformly distributed. This means that even within a single device, some fingers may receive dramatically less UV energy than others.

Think about what this means in practice. Two salons on the same street, using the same gel polish, can get completely different levels of cure simply because of the lamp they use. One may achieve a safe, full cure. The other may send clients home with undercured product on their nails â product that looks fine but is still releasing allergenic chemicals.

Shipp LR, Warner CA, Rueggeberg FA, Davis LS. Further investigation into the risk of skin cancer associated with the use of UV nail lamps. JAMA Dermatology. 2014;150(7):775â776.

WHY DO LAMPS VARY SO MUCH?

There are three main reasons:

1. Wavelength mismatch

Every gel formula contains chemicals called photoinitiators â these are the ingredients that absorb UV light and trigger the curing (polymerisation) reaction. Different photoinitiators absorb light at different wavelengths. Some need UV-A light at around 365 nm, others at 405 nm, and many modern formulas need both.

An older LED lamp that only emits 405 nm light simply cannot activate a photoinitiator that absorbs at 365 nm. The product may appear to harden on the surface, but the deeper layers remain uncured. Research shows that even a 20 nm deviation from the photoinitiator's peak absorption wavelength can reduce curing efficiency by 50% or more.

2. Insufficient power (irradiance)

As the JAMA Dermatology study showed, the power output of nail lamps varies enormously. Cheap lamps, ageing bulbs, and poorly designed reflectors all contribute to low irradiance. A lamp's advertised wattage is not a reliable indicator of how much UV energy actually reaches the nail plate.

3. No industry standards

There is currently no agency in the US, UK, or EU that certifies or standardises the UV output of nail lamps. No one tests whether a lamp actually delivers what it claims. This means low-quality, counterfeit, or degraded lamps remain in widespread use with no oversight.

THE 50% PROBLEM: WHY "LOOKING CURED" ISN'T ENOUGH

Here is something that surprises many technicians: UV-cured gel can look and feel completely cured at only 50% polymerisation. The surface appears hard and glossy, the client is happy, and the technician assumes everything is fine.

But beneath that shiny surface, up to half of the chemical monomers may remain unreacted. After the client leaves the salon, the product may cure an additional 4â6% at most. To be considered safely and fully cured, gel products need to reach approximately 90% polymerisation or higher. Anything less means residual monomers â the very chemicals that cause allergies â remain in the product, in contact with the nail and surrounding skin.

THE ALLERGY CONNECTION: WHAT THE RESEARCH SHOWS

The link between undercuring and allergic contact dermatitis is now well established in the dermatology literature.

HEMA: the main culprit

HEMA (2-hydroxyethyl methacrylate) is the most commonly used monomer in gel polish formulations and the most frequent cause of nail product allergies. A comprehensive review published in Contact Dermatitis (Groot et al., 2023) confirmed that HEMA is safe once fully polymerised â but when curing is incomplete, residual monomers can induce allergic contact dermatitis.

HEMA has a molecular weight of just 130 g/mol. Substances below 500 g/mol can penetrate the skin barrier. This means that every time a client with undercured gel washes their hands or showers, uncured HEMA can leach through the nail plate and into the surrounding skin. Over repeated exposures, this can sensitise the immune system.

Groot AC et al. 2-Hydroxyethyl methacrylate (HEMA): A clinical review of contact allergy and allergic contact dermatitis. Contact Dermatitis. 2023;89(6):401â433.

The numbers are alarming

An eight-year retrospective study at Amsterdam UMC (Steunebrink et al., 2024) identified 67 women diagnosed with allergic contact dermatitis from nail cosmetics between 2015 and 2023. Of these, 97% tested positive to HEMA on patch testing. The authors identified undercuring â from wrong lamp choice, insufficient cure times, or poor-quality formulas â as a primary pathway to sensitisation.

Steunebrink et al. Contact allergy to acrylate-containing nail cosmetics: A retrospective 8-year study. Contact Dermatitis. 2024.

EU legislation hasn't solved the problem

In 2021, the EU introduced legislation restricting HEMA and di-HEMA TMHDC in nail products. However, a 2025 multi-centre audit across seven European dermatology centres (Wilkinson et al.) found that allergy rates have not decreased. The reason? The problem was never the ingredient itself â it was always the curing process. The authors called for an urgent review of the regulatory approach.

Wilkinson SM et al. Contact allergy to methacrylate containing nail products: Lack of impact of EU legislation. Contact Dermatitis. 2025;92(4):283â290.

THE LIFELONG CONSEQUENCES

Acrylate sensitisation is not just a nail industry problem. Once a client becomes allergic to methacrylates, they may develop lifelong cross-reactivity to acrylates found in:

• Dental fillings and bonding agents
• Orthopaedic bone cements (joint replacements)
• Medical adhesives (insulin pump patches, glucose monitors)
• Contact lenses

This is why undercuring is not just a cosmetic issue â it is a health issue with potentially serious consequences for your clients' future medical care.

WHAT YOU CAN DO

The good news is that this problem is entirely preventable. Here are the steps every nail technician should take:

Use the lamp recommended by your product manufacturer

Every reputable gel manufacturer designs and tests their products with specific lamps. Using the recommended lamp ensures the correct wavelength and irradiance for full cure. If the manufacturer doesn't specify a lamp or provide curing data, consider whether you should trust the product at all.

Never assume a third-party lamp will work

Cheap, unbranded lamps bought online are one of the biggest risk factors. As the Shipp et al. study demonstrated, there is enormous variation even among lamps found in professional salons. A lamp that "worked fine" with one brand may dramatically undercure another.

Perform cure tests

After curing, press firmly on the gel surface with a lint-free wipe. If any product transfers or feels tacky beneath the inhibition layer, the cure is incomplete. Some professional bodies, such as HONA, publish detailed cure-testing protocols.

Replace ageing bulbs

UV fluorescent tubes degrade over time and lose power even though they still appear to light up. LED lamps are more stable but can also degrade. Follow the manufacturer's guidance on lamp replacement intervals.

Choose hypoallergenic products

Products formulated without high-risk monomers like HEMA, HPMA, and di-HEMA TMHDC significantly reduce the risk of sensitisation â even if a slight undercure does occur. Prevention is always better than cure.

THE BOTTOM LINE

The gel isn't the villain â undercuring is. A properly matched lamp and verified cure makes gel products safe. But using any random lamp and assuming it works is gambling with your clients' health. The published science is clear: lamp-product compatibility matters, and getting it wrong can cause allergies that last a lifetime.

As professionals, we owe it to our clients to understand this. The research is there. The solutions are straightforward. The only question is whether we choose to act on them.

References

1. Shipp LR, Warner CA, Rueggeberg FA, Davis LS. Further investigation into the risk of skin cancer associated with the use of UV nail lamps. JAMA Dermatology. 2014;150(7):775â776.
2. Groot AC et al. 2-Hydroxyethyl methacrylate (HEMA): A clinical review of contact allergy and allergic contact dermatitis â Part 1. Contact Dermatitis. 2023;89(6):401â433.
3. Steunebrink et al. Contact allergy to acrylate-containing nail cosmetics: A retrospective 8-year study. Contact Dermatitis. 2024.
4. Wilkinson SM et al. Contact allergy to methacrylate containing nail products: Lack of impact of EU legislation. Contact Dermatitis. 2025;92(4):283â290.
5. Axler EN, Lipner SR. Unveiling an acrylate allergy epidemic: Analysis of dermatologic findings associated with at-home gel nails on TikTok. Journal of Cutaneous Medicine and Surgery. 2024.
6. Ford H et al. Quantifying the ultraviolet radiation emitted by nail curing devices: A descriptive study. Australasian Journal of Dermatology. 2021;62(2):e311âe313.