Shellac Nails and Risk of Skin Cancer

Feb 26, 2024

Dear Editor

Launched in 2010, the Shellac nail is one of the world’s latest trends which is growing exponentially in popularity. While its cosmetic value has been advertised extensively, little is discussed regarding its potential risks- namely, melanoma and NMSCs.

Shellac is a substance secreted by the female lac bug which is most commonly found in forests in India. During certain seasons of the year, this insect begins to suck sap from lac trees while simultaneously propagating approximately 1000 eggs. The lac insect absorbs the sap until it dies- a process known as the “feast of death”. The digested tree sap is subsequently secreted through its pores and on contact with air, it forms a hard shell-like covering over the entire swarm, providing a medium to allow the larvae to mature. This lac resin is a natural polymer, and is subsequently scraped from the trees. It is refined by being melted down and filtered before being dried into flat sheets. To use the shellac, the flat sheets are ground into powder and dissolved in alcohol to achieve a liquid of the desired concentration- in this case, for the manufacturing of shellac nail polish.[1]

Ultraviolet radiation from a UV Shellac Lamp is required in order to cure the shellac nail polish once it is applied to the nail. This polish contains a photoinitiator. Once exposed to UV light, the photoinitiator reacts to the UV and releases free radicals. These free radicals then initiate polymerisation/cross linking reactions. Polymerisation enhances stabilisation and the subsequent solidification of the shellac nail polish onto the nail. [2] Polymerisation is an exothermic reaction, therefore, during this process, the recipient will often experience a burning/hot sensation. [3]

UV radiation is divided into 3 main types according to its wavelength- UV-A (400-315 nm), UV-B (315-280 nm) and UV-C (280-200 nm). The shorter the wavelength, the more harmful the radiation, however, all forms of UV radiation increase your risk of malignancy. As sunlight passes through the atmosphere, all UV-C and most of the UV-B is absorbed by ozone. However, as the ozone layer becomes increasingly thinner, people are being exposed to higher levels of UV radiation, especially UV-B. UV-A is not filtered significantly by the atmosphere and accounts for 95% of the UV radiation that reaches the earth’s surface. Long-wave UV-A reaches the skin’s dermis and causes premature ageing, e.g. wrinkling and solar lentigo. Medium wavelength UV-B only reaches the epidermis but is very biologically active and is responsible for sunburn. UV-C is the most lethal of ultraviolet radiation. [4] UV-C is strongly absorbed by the DNA of micro-organisms, disrupting nucleic acid replication and rendering that micro-organism non-viable. [5] Extreme damage may ensue if exposed to UV-C, e.g. severe burning of the skin and eyes (photokeratitis). Thankfully, natural UV-C does not reach the earth’s surface as aforementioned, but man-made sources of UV-C are available to us, e.g. welding torches and xenon/mercury lamps.

Similar to sunbeds, most of the radiation emitted from shellac UV lamps is UV-A, and the typical wavelength used varies between 365-370 nm. [6) Exposure time per session is typically 5 minutes per hand with repeated treatments every 2-3 weeks.

A limited number of studies have shown that shellac nails do not produce a significantly increased lifetime risk of developing skin cancer and that dermatologists and primary care physicians may reassure patients regarding the safety of these devices. [6] Conversely, other studies have shown that the UV rays emitted by these lamps are 4.2 times stronger than the sun’s UV rays and thus are a cause for concern. [7] Additionally, subungual melanoma often presents as a delayed diagnosis, particularly when it affects the toe and some of these tumours have already metastasised at the time of diagnosis. [8]

In truth, the risks associated with these lamps have yet to be established as it is a relatively new phenomenon. Lack of regulations exist surrounding UV shellac lamps, but a lack of studies exists also regarding their potential to cause a future epidemic in human skin cancers. More research is needed to evaluate the carcinogenic effects of high dose UV-A irradiation to human skin. In the interim, a sensible suggestion would be to apply sun cream before a trip to the salon and to wearing fingerless gloves during the session.

References-

1. http://www.madehow.com/Volume-4/Shellac.html

2. https://edu.rsc.org/feature/polished-polymers/3007359.article

3. Dina Ciccarelli. Tech Support: What are Heat Spikes? nailpro.com Aug 7th, 2018

4. https://www.who.int/news-room/q-a-detail/radiation-ultraviolet-(uv)

5. Dai T, Vrahas MS, Murray CK, Hamblin MR. Ultraviolet C irradiation: an alternative antimicrobial approach to localized infections?. Expert review of anti-infective therapy. 2012 Feb 1;10(2):185-95.

6. Markova A, Weinstock MA. Risk of skin cancer associated with the use of UV nail lamp. The Journal of investigative dermatology. 2013 Apr 1;133(4):1097.

7. 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. Journal of the American Academy of Dermatology. 2013 Dec 1;69(6):1069-70.

8. https://dermnetnz.org/topics/melanoma-of-nail-unit/

Competing interests: No competing interests