Are gel nails bad for you? UV, skin cancer and allergies | Lab Muffin Beauty Science (2024)

If you’ve ever tried gel nails, you’ll know you have to bake your fingers under a UV lamp. And if you’re like me, you might’ve thought: I know UV from the sun is bad and causes skin cancer, tanning beds are extra bad, they cause extra skin cancer… is this thing that looks like a tanning bed (for ants) actually safe?

We’re getting to the bottom of this today.

The video version is here, keep scrolling for the article…

UV wavelength and dose

First, a quick refresher on UV. UV is a form of light that’s more energetic than the visible light that we can see, and our main source of exposure is the sun. It’s the part of sunlight that causes skin cancer, sunburn, premature skin aging, and uneven pigment.

When it comes to the dangers of UV, we need to think about 2 things: wavelength and dose.

Wavelength

Sunlight has two types of UV. UVA has longer wavelengths, and UVB has shorter wavelengths, but we’re going to think of these as tiny particles called photons.

UVB photons have higher energy. They smash into things harder, but they don’t get as deep into skin. UVA photons are lower energy and cause less direct damage.

So which one is more damaging? That’s not a trick question – it’s UVB.

It’s like getting punched. UVB is a really hard punch, with more energy, UVA is … less hard, with less energy. They both contribute to skin cancer and premature skin aging, but different amounts and in different ways.

Within each category, there’s still a range of effects. Some UVA is higher energy and almost UVB (it contributes to sunburn), but some UVA is lower energy and is basically just purple light.

Dose

The other big thing that matters is dose. This is how much UV your hands are getting, which depends on the intensity of UV from the lamp (irradiance), and how long your hands are in there (exposure time).

If you’ve seen my posts before, you’ll know “the dose makes the poison” comes up a lot with ingredient safety, and it’s important for UV safety too. One punch might not do much, but 1000 punches is very different – more means more damage.

So what wavelengths and doses are we from these lamps? Well, we need to talk about why we have UV in the first place…

How gel polish works

Gel polish uses UV in a cool and clever way.

Regular nail polish contains polymers like nitrocellulose, which are long-chained molecules. These come together to form a solid layer on your nails as the solvent evaporates and the polish dries.

But at some point, nail scientists realised creating the polymers on your nails – putting the little building blocks on the nail, and joining them into a chain afterwards – helps it last a lot longer.

There are three main categories of these longer-wearing nail products: acrylics, gels, and dips (my book The Science of Beauty talks more about how these products work, as well as about 100 other topics!).

Related: The Science of Beauty

Some of the building blocks (monomers) inside a typical gel polish include”

• HEMA (2-hydroxyethyl methacrylate)
• Isobornyl methacrylate
• Di-HEMA trimethylhexyl dicarbamate
• Bis-HEMA IPDI

They have double bonds (shown in pink), which means a chain reaction can join them together, like a row of dominoes falling.

When the first monomer is triggered, one of the bonds in its double bond can move to join to another monomer. This triggers Monomer 2, and its bond moves to join to Monomer 3, and so on until you get a long chain (the polymer).

It’s a chain reaction that actually makes a chain!

But how do you make sure the monomers don’t join up too early in the bottle and make a giant clump, but do join up quickly after you put it on your nails?

The answer is different for each type of longwear product – for gels, it’s UV.

As well as building blocks, gel polishes contain initiators, such as:

• Hydroxycyclohexyl phenyl ketone
• Ethyl trimethylbenzoyl phenylphosphinate
• Trimethylbenzoyl diphenylphosphine oxide

They break up in UV, and turn into little triggering molecules with unpaired electrons (free radicals). These can attack a building block and start off the polymerisation chain reaction, like your finger pushing over the first domino. Without UV, gel products wouldn’t harden and “dry”.

But there’s an added complication with UV risk. Gel products have different mixtures of building blocks and initiators, which activate differently depending on UV wavelength and dose. The combination of all these is carefully optimised so the product reacts at the right speed.

If the gel reacts too quickly, the reaction produces too much heat which is painful, and can make your nails to separate from the nail bed (really painful and can lead to infections).

But if it reacts too slowly, it might not cure completely. Some building blocks can stay unreacted on the nail, which is also a bad outcome (foreshadowing).

In both cases, thecured product is less optimal, and might crack or chip more easily. That’s why you’re meant to use the lamp specifically designed for a particular brand of gels, and why there are so many different nail lamps with varying UV outputs.

UV lamp studies

Gel polishes surged in popularity around 2010, which is when people really started wondering about the safety of tiny-tanning-bed-looking-things. There are now quite a few studies measuring the wavelengths and doses of UV your hands get from a range of nail lamps (see bottom of article for summary table).

The researchers come from a range of backgrounds, including:

• Nail industry scientists, who do have an obvious conflict of interest (Schoon, Bryson and McConnell are from the brands CND, OPI and Light Elegance)
• Scientists with a long and impressive track record of sun protection research (Diffey created the Boots Star UVA rating system, and Dowdy and Sayre did a lot of work on testing sunscreens with UV lamps, so they know UV lamps very well)
• Academic scientists with no ties to the nail industry (Baeza et al. actually tested the most lamps)
• Dermatologists (Markova & Weinstock, Curtis et al., Shipp et al.)
• Government scientists from the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) (Ford et al.)

Their conclusions are all pretty similar.

Which wavelengths?

There are two main types of gel nail lamps:

• “UV lamps” have fluorescent bulbs which look tubes
• “LED lamps” have LED bulbs that look like flat little squares or dots, and were introduced more recently

Both types produce UV, even though it kind of sounds like LED lamps don’t (I would like to know who picked these names – I just want to talk). I’ll be referring to “UV lamps” as “fluorescent lamps”, because that actually makes sense.

To make it more confusing, some lamps contain both fluorescent and LED bulbs – I’m calling these “combo lamps”.

Fluorescent bulbs tend to produce a wider range of wavelengths (mostly UVA, but also a tiny bit of UVB, and some visible light), while LED bulbs produce a narrower range of wavelengths, mostly at a longer wavelength (almost entirely UVA, and a lot of visible light).

This graph from Dowdy and Sayre illustrates this nicely – a higher peak means more of that wavelength. From left to right:

• There’s almost nothing in the UVB region (you can only see it in the expanded log-scale version of the graph, which is also in the paper)
• The three fluorescent lamps have their biggest peak at about 370 nm
• The three LED lamps have a bigger hump but it’s at about 400 nm, so the peak is straddling UVA and visible light

What doses?

Now let’s look at the doses of these wavelengths.

All of the studies found minimal UVB, which is reassuring because UVB directly damages DNA, and is more strongly linked to skin cancer.

A newer 2018 study by Baeza and coworkers tested the most lamps – most lamps had irradiances below 0.025 W/m², and they all produced far less intense UVB than you’d get from the sun in winter in Barcelona (0.10 W/m²).

But UVA is a different story. UVA is less directly damaging, but it knocks electrons off things to form free radicals. We want this to happen in gel polish, but chain reactions in skin contribute to skin cancer and accelerated skin aging.

About a third of the lamps tested by Baeza produced more intense UVA than the midday summer sun in Barcelona (UV index 9, dark grey line), and some were more than twice as strong (green line) (each dot is a lamp):

This chart also shows the different types of lamps. The LED lamps they tested (blue outlines) are a safer option in terms of total UV intensity. That’s probably because they mostly produce longer wavelengths, which are less energetic to begin with – a lot of the energy they produce is in the visible region.

At this point you might be thinking LED lamps seem to be the perfect solution – I can get less UVA if I just use the lamps with the knobby dotty lights, right?

I thought this at first too, but unfortunately, not necessarily. There’s a newer study from ARPANSA that looked at 7 LED lamps and 1 fluorescent one. Here’s what they look like on the same graph, assuming the measurements are roughly comparable – LED UVA irradiances can get quite high:

Conflicts of interest, appropriate study designs

This brings me to a little tangent about conflicts of interest that’s crucial to interpreting beauty science studies, and it took me a while to figure out.

There’s a general perception that a conflict of interest automatically means a study is unreliable. But there’s a less obvious downside to a lot of cosmetic science studies by independent researchers, with no conflicts of interest.

Their studies are often not designed well, or not interpreted well, because the researchers only looked at the peer-reviewed literature when trying to understand the area. This is a problem because there isn’t much incentive to publish cosmetic science in peer-reviewed journals (I talked about this in my post about retinol). There also isn’t that much public funding, so you also see a lot of independent studies with tiny sample sizes, for instance.

Related post: Is Retinol a Scam? The Science

This trend becomes really apparent once you’ve read enough papers, and I’ve talked about a few not-great studies by independent scientists before: rosemary oil and hair loss, chemical sunscreens killing coral, zinc oxide inactivating chemical sunscreens, and a whole bunch of tranexamic acid studies.

There are some here as well. Two of the studies by dermatologists used the wrong type of spectrometer (an instrument for measuring light). Two of the very experienced sun exposure scientists point this out in their papers – they work in a light testing lab, and they do have patents on UVA lamps used for medical treatments, which is a conflict of interest.

But this mistake meant that the dermatologists were underestimating UV, so the scientists’ results were going against their conflict of interest.

This isn’t a blanket rule. The newest two studies didn’t have conflicts of interest and used the right type of spectrometer (from what I can tell anyway, as a chemist who used spectrometers a bit, but not to the point where I can spot this sort of issue easily in a paper). One study sent the lamps to an accredited measurement lab, and the other has authors from the official Australian radiation agency, so they’re probably reliable.

And of course, there are questionable papers by researchers with conflicts of interest too: the Valisure benzene studies, the Colorescience powder sunscreen study, and the bakuchiol study.

Basically, there are no blanket rules when it comes to conflicts of interest and how sus a study is, especially in an area without much public funding like cosmetic science.

Lamps and skin cancer

So far, we have a bunch of lamps putting out more intense UVA than the sun at UV index 9. And while decades of exposure to very short, intense bursts of UVA could have effects we don’t know much about yet, there’s a lot of evidence that points towards this not being a massive concern.

Exposure times are short – usually less than 10 minutes every few weeks, so the total UVA energy hitting your skin is maybe maximum 20 minutes of midday sun in summer in Barcelona (UV index 9).

This is actually safer than it sounds, because we need to take into account the damage from specific wavelengths. UVA is a range, with harder and softer “punches”. One hard punch might break your nose, but two punches half as hard might not, even if the total energy is the same. Longer UV wavelengths are generally much, much less harmful, and that’s what nail lamps use.

Some studies estimated the biological impact using an action spectrum. This essentially means they weighted different wavelengths based on how much they contribute to damage. For example, in this spectrum, 300 nm (relative impact of 1) punches about a thousand times harder than 350 nm (impact of <0.001):

Different studies have calculated non-melanoma skin cancer risk in various ways, and they’re all very low:

Diffey (2012), 1 fluorescent lamp (2 x 9W bulbs):

• Sunlight is 1.7 times more carcinogenic
• 1 additional SCC case in 44,000 to 396,000 people, after 5 to 40 years of manicures every 3 weeks (8 minutes total exposure)

Dowdy and Sayre (2013), 3 fluorescent and 3 LED lamps:

• Non-melanoma skin cancer risk is 11 to 46 times less than overhead sunlight, and 3 to 12 times less than mid-angle sunlight
• It would take 2.4 to 22.4 hours to reach the FDA’s maximum daily exposure time for tanning beds (versus <10 minutes of exposure for a manicure)

Baeza and coworkers (2018), 22 fluorescent, 3 combo and 3 LED lamps:

• UV index (reflects erythemal UV, mostly UVB) is less than 2, which is noon in winter in Barcelona

Ford and coworkers (2021), 7 LED and 1 fluorescent home lamps:

• It would take 38 to 197 minutes to reach the IRPA/ICNIRP occupational exposure limits for UV

On top of that, the backs of your hands are less sensitive to UV – one study measured that they needed about 4 times more UV to burn than the cheek.

Case reports

There have been a few case reports of people developing skin cancers on their hands after lots of gel manicures. However, the manicures didn’t necessarily cause the cancer. Case reports aren’t really scientific evidence, and are just meant to be a way for doctors to flag interesting cases to inspire further research – it’s a form of anecdotal evidence, but nicely written up.

Related post: Science vs Anecdotal Evidence and Reviews

An extra factor was involved in most of these cases. For example:

This person was taking a photosensitising medication, and had been getting UV manicures for 10 years

This person had been getting manicures for 18 years, and using a tanning bed every week

These two cases didn’t have anything reported other than UV manicures, but the first case was using the UV lamp to dry normal nail polish. UV doesn’t speed that up by much, so I’m guessing they were just using it for the fan, and the polish still takes ages to dry. So she was probably getting much higher UV exposure than normal.

A lot of their exposure was also probably from older fluorescent lamps that put out more UVB, and the types of skin cancers they got are the ones more associated with shorter wavelengths.

Lamps and skin aging

What about skin aging, the other big effect of UV?

One study looked at skin sagging and elastosis (when UV from the sun messes up the elastin in your skin, leading to deep wrinkles and texture). Elastosis is worse with shorter wavelengths, but UVA at 340 nm is actually the worst for sagging (higher line means worse):

Here’s what it looks like compared to summer (dark grey line) and winter (light grey line) midday sun. Most lamps are causing these effects less intensely than midday summer sun. A handful are worse, but the highest is only about double the intensity (again, exposure time is important, so the worst translates to about 20 minutes of midday summer sun every 3 weeks).

Again, you might be thinking – if I just go for LED lamps, I’m only getting the longest wavelength, least damaging UVA (the outline squares are very low). But unfortunately, we also don’t have an easy solution here.

The older studies on salon lamps only reported a peak at 400 nm, which translates to lower effects. But, again, the Australian study with home devices bucks the trend, and the data is tucked away in the supporting information:

5 out of 7 of the LED lamps tested are putting out shorter wavelength UVA (around 370 nm), which matches the main fluorescent peaks in the older studies. I would guess this would also apply to some salon lamps.

Melanoma cases?

I mentioned non-melanoma skin cancer before, so you might’ve been thinking: what about melanoma?

There aren’t any case reports of melanoma with UV manicures, so none of the studies really looked at that. Linking UV wavelengths to melanoma is also more complicated, so estimates with action spectra aren’t very useful.

However, this study looked at population-level (epidemiological) data in the US. There’s been no increase in melanoma from 2007 to 2016, and actually a slight decrease in 15-39 year olds from 2006 to 2016. The locations of the melanomas aren’t tracked, but this suggests that so far, it isn’t a big problem.

What should you do?

This is all pretty reassuring, but the papers do suggest some simple steps you can take to lower your risk even more, if you get gel manicures regularly and you’re worried:

• You can wear gloves without fingertips to cover your skin
• You can put sunscreen on your hands before the gel manicure, then clean the sunscreen just off your nails
• Don’t look at the UV lamp while it’s on
• If you’re taking medications that increase your light sensitivity, or if you have other risk factors (e.g. previous skin cancers), don’t get gel manicures
• Check your hands for suspicious spots, especially if they change over time, and see a specialist once you notice them

You don’t need to worry much about your nail beds – the nail blocks all the UVB and almost all UVA, and the gel blocks even more. (It’s still worth checking for spots though, since there can be cancers there that aren’t linked to UV exposure.)

New studies?

Once in a while you’ll see nail lamps and cancer pop up on the news and social media. The last few times it was because of scary-sounding studies like this one in 2023, which led to news stories about mutations linked to cancer.

This was an in vitro study, where cells on plates were placed in a nail lamp. The scientists saw mutations also found in some skin cancers.

However, this is a hazard experiment that shows changes that could happen. It doesn’t show changes that are likely to happen if we take dose into account – these cells are getting much higher doses than normal:

• Cells in our hands are under layers of dead skin cells which block a lot of UV
• Cells don’t behave the same in our skin versus in a petri dish
• This experiment irradiated the cells for 20 minutes continuously, then another 20 minutes on the same day, which is a lot longer than a typical gel manicure (the manufacturer recommends 60 second cures, which translates to about 5 minutes per hand – their exposure time would be for 8 manicures in a single day).
• The article makes little reference to the quantity of mutations the cells are getting.

Some of these limitations were mentioned in the study, but they didn’t reference earlier studies with more reliable dose measurements. The authors also weren’t clear about the limitations in media interviews – they say these results are “alarming”, and that theydon’t get gel manicures anymore.

Some journalists asked other scientists to comment, who gave far more context, such as in this Sydney Morning Herald article (shoutout to the wonderful Hannah English who sent this to me!):

• “To be honest, the results are not surprising,” said Professor Richard Scolyer, co-medical director of Australia’s Melanoma Institute. “We know these devices emit UVA. And UVA can cause DNA damage. We just don’t know how it translates to humans.” [Note: “not knowing” is quite specific in scientific terms – we know quite a lot about UVA in general, just not specifically with UV nail lamp exposures.]
• UVA is known to pose a cancer risk. But nail dryers have been widely used for some time and, despite that, cancer of the finger remains extremely rare, said Professor David Whiteman, a cancer epidemiologist based at Queensland’s QIMR Berghofer medical research institute. “If I went out now in the sun without sunblock and then took a skin biopsy, in five minutes I’d have a lot more damage than those cells did,” he said.
• In 2021, the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) conducted tests of eight at-home UV nail dryers. Even the most powerful device tested would need to be used for almost 40 minutes before it started posing a risk, the agency found. Most nail dryers are only used for a few minutes at a time.
• Associate Professor Ken Karipidis, the agency’s spokesman, admitted “the physiological impact of the accumulated UVA exposure to the hands remains unknown”. “For that reason, the ARPANSA recommendations are advised such as opting to use fingerless gloves and/or sunscreen, and the provision of safety information for consumers about the possible risks.”

(Side note: I met Professor David Whiteman at a sun protection conference I spoke at recently! He’s super nice, and he also spoke at our BeautySciComm mythbusting campabout sunscreen.)

Related: BeautySciComm Mythbusting Camp

A scarier risk

There is an actual scarier risk with gel manicures: allergies.

Allergies might sound like a mild annoyance, but they can be a big deal, and it’s the thing I actually take more precautions with when using gel or dip.

Acrylics, gels and dips all use acrylate monomers as the building blocks. After the product is cured, the monomers are joined into a large chain which doesn’t get into your skin easily, so it isn’t a big problem. But when the monomers aren’t joined up, they can get into your skin.

You can develop an allergy if you’re exposed to the monomers enough, and further exposure can cause swelling, blisters, itching, and rashes. These can occur around your nails, as well as places you touch with your nails, like your eyelids and face.

The larger issue is that acrylates aren’t only used for nail products. They’re quite widespread, and are used for sticking bones together in orthopedic surgery, and a whole bunch of dental materials. If you have an allergy, you might end up reacting to a filling, for example, which is pretty horrific.

(Fun fact: OPI stands for Odontorium Products Inc – they actually started as a dental acrylics company before switching to nail acrylics.)

How to minimise allergies

There are many nail resources that go into more detail, but essentially you want to minimise any exposure to the uncured gel.

Your nails are generally not the problem, since they’re pretty resistant – you only really need to worry if your nails are really thin or cracked.

The main source of exposure is skin:

• Try to avoid getting uncured monomer on the skin around your nails (paint within the lines) – don’t be as messy as you might be with regular polish
• Cure the polish properly – use the lamp matched to the product you’re using, follow the curing times, and don’t use too little UV because you’re worried about excess UV exposure
• Applythin layers, so the UV can reach all of the gel
• Don’t touch the sticky layer on top of the gel, which comes from monomers that aren’t surrounded by enough other monomers to react properly
• Make sure your lamp is clean and maintained, since things like dust can lower the UV reaching your nails

Because it’s harder to do your own nails neatly, it’s generally less risky to get gel manicures from a properly trained nail tech. There’s been a huge rise in acrylate allergies because of home gel kits, especially after lockdown when everyone was doing their nails at home.

Nail studies summary table

References

Schoon DD. Cosmetic Prostheses as Artificial Nail Enhancements. In: Draelos ZD, ed. Cosmetic Dermatology: Products and Procedures. 3rd ed. Wiley; 2022:289-298.

Schoon D, Bryson P, McConnell J. Do UV Nail Lamps Emit Unsafe Levels of Ultraviolet Light? November 2012.

Zhivagui M, Hoda A, Valenzuela N, et al. DNA damage and somatic mutations in mammalian cells after irradiation with a nail polish dryer. Nat Commun. 2023;14(1):276. doi:10.1038/s41467-023-35876-8

Ford H, Horsham C, Urban D, Tinker R, Hacker E. Quantifying the ultraviolet radiation emitted by nail curing devices: A descriptive study. Australas J Dermatol. 2021;62(2). doi:10.1111/ajd.13539

Schwartz CT, Ezaldein HH, Merati M. Ultraviolet light gel manicures: Is there a risk of skin cancer on the hands and nails of young adults? J Clin Aesthet Dermatol. 2020;13(7):45-46.

Ratycz MC, Lender JA, Gottwald LD. Multiple dorsal hand actinic keratoses and squamous cell carcinomas: A unique presentation following extensive UV nail lamp use. Case Rep Dermatol. 2019;11(3):286-291. doi:10.1159/000503273

Baeza D, Sola Y, Del Río LA, González R. Nail dryer devices: A measured spectral irradiance and labelling review. Photochem Photobiol Sci. 2018;17(5):592-598. doi:10.1039/c7pp00388a

Sola Y, Lorente J. Contribution of UVA irradiance to the erythema and photoaging effects in solar and sunbed exposures. J Photochem Photobiol B. 2015;143:5-11. doi:10.1016/j.jphotobiol.2014.10.024

Dowdy JC, Sayre RM. Nail curing UV lamps: Trivial exposure not cause for public alarm. J Am Acad Dermatol. 2015;73(5):e185-e186. doi:10.1016/j.jaad.2015.06.064

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 Dermatol. 2014;150(7):775. doi:10.1001/jamadermatol.2013.8740

Markova A, Weinstock MA. Risk of skin cancer associated with the use of UV nail lamp. J Invest Dermatol. 2013;133(4):1097-1099. doi:10.1038/jid.2012.440

Dowdy JC, Sayre RM. Photobiological safety evaluation of UV nail lamps. Photochem Photobiol. 2013;89(4):961-967. doi:10.1111/php.12075

Curtis J, Tanner P, Judd C, Childs B, Hull C, Leachman S. Acrylic nail curing UV lamps: High-intensity exposure warrants further research of skin cancer risk. J Am Acad Dermatol. 2013;69(6):1069-1070. doi:10.1016/j.jaad.2013.08.032

Diffey BL. The risk of squamous cell carcinoma in women from exposure to UVA lamps used in cosmetic nail treatment: SCC and UVA nail lamps. Br J Dermatol. 2012;167(5):1175-1178. doi:10.1111/j.1365-2133.2012.11107.x

MacFarlane DF, Alonso CA. Occurrence of nonmelanoma skin cancers on the hands after UV nail light exposure. Arch Dermatol. 2009;145(4). doi:10.1001/archdermatol.2008.622

Freeman C, Hull C, Sontheimer R, Curtis J. Squamous cell carcinoma of the dorsal hands and feet after repeated exposure to ultraviolet nail lamps. Dermatol Online J. 2020;26(3):13030/qt1rd1k82v.

Mannix L. In the lab, nail dryers damage cells. But what about in the salon? The Sydney Morning Herald. January 27, 2023.

Connor K. In cells, UV-emitting nail polish dryers damage DNA and cause mutations. ScienceDaily. January 17, 2023.

Guenther J, Norman T, Wee CP, Adler BL. A Survey of Skin Reactions Associated With Acrylic Nail Cosmetics, With a Focus on Home Kits: Is There a Need for Regulation? Dermatitis. 2024;35(1):49-54. doi:10.1089/derm.2023.0204