So, after a wonderful sunny Easter weekend, my Facebook feed is now filled with selfies of individuals who have “caught the sun”. Let us discuss.
What is sun burn?
Unlike normal burns, which are caused by infrared radiation, sun burns are caused by ultraviolet radiation. Sun burn itself is essentially a combination of two different reactions: there’s the more superficial damage that results in localised activation of the immune system, leading to inflammation and immune infiltration in that area – this is what causes those really characteristic sunburn features: redness, heat, swelling and pain. The second part is the deeper DNA damage that goes on under the surface (Guerra and Crane, 2019).
Sunburn is most common in young adults, those who apply tanning products, are physical active, binge drinkers or the overweight/obese (Holman et al., 2018).
What is ultraviolet radiation?
There are three types of UV radiation:
UVC is the most powerful (or most energetic), but we’re protected from this by the Earth’s atmosphere.
UVB is middle of the range and can penetrate the atmosphere. These can breach the deeper layers of the skin and damage cellular DNA and are the most common cause of skin cancers and sun burn.
UVA is the least energetic, but still harmful. These rays cannot penetrate through the outer layers of skin, but still damage what it can reach; they are largely implicated with the breakdown of collagen, making the appearance of wrinkles more pronounced and contributing to ageing. They are still linked to skin cancer.
The strength of the UV varies greatly depending on the season, time of day and location. The levels of UV at any time are quantified using the UV index, which runs from 1 to 11 with the higher numbers denoting stronger radiation. Most weather apps will show the forecast UV (American Cancer Society, 2017).
So what’s a tan?
Getting a tan unfortunately, despite being considered attractive in certain cultures, does mean that the skin has experienced some damage. Melanocytes in your skin start producing melanin in response to UV radiation; this is a pigment that is able to absorb UV, protecting the body from further exposure (British Association of Dermatologists, 2019).
What’s the damage?
UVB induces a chemical reaction in DNA to form something called a pyrimidine dimer, changing nucleotide pairings (thymine and cytosine) so the DNA reads incorrectly. During exposure to sunlight, 50-100 of these mutations can happen every second in each cell, but your bodies own repair mechanisms will fix most of these straight away through a process called nucleotide excision repair (Goodsell, 2001).
However, it’s the ones that get away that can be deadly. While roughly 90% of DNA is lovingly termed ‘junk’ and the UV induced mutations themselves are completely random in location, all it takes a few missed changes to the DNA that codes for proteins that control the cell cycle and you’ve potentially got yourself a new baby cancer cell (Rands et al., 2014; Visconti, Della Monica and Grieco, 2016).
- High UV radiation
- Medications: tetracyclines, retinoids, steroids, NSAIDs, some diuretics, St John’s Wort
- Lighter skin tones (Guerra and Crane, 2019)
What’s the issue?
Due to all of the above mechanisms, increased exposure to the sun increases the risk of skin cancer developing. Skin cancer is currently the fifth most common cancer diagnosis in the UK (this excludes non-melanoma skin cancer). Nearly 14,000 new cases of melanoma were diagnosed in 2016, with a further 130,000 non-melanoma skin cancers reported although they state that this number is likely to be an underestimate. The South-West holds the second highest diagnosis rate just after the South-East (Office for National Statistics, 2018).
Now what’s this suncream business?
Suncream contains particular chemicals that protect the body from UV radiation, preventing it from damaging the skin underneath. There are two types of sun protectants: physical blockers and chemical absorbers. These depend on their chemical makeup and each group have their own properties; this video by Aussie Dermatologist Dr Lim explains the difference between them really well.
Sun Protective Factor (SPF) is the current industry standard of protection given by sun creams and is regulated by the EU. An SPF of 15 will block approximately 93% of UVB, with SPF of 50 blocking around 98%; this however doesn’t include UVA radiation, which is currently rating by a star system (Dale Wilson, Moon and Armstrong, 2012).
Conversations about suncream and skin cancer aren’t common for nurses unless you’re working in a really niche area, but that doesn’t mean you shouldn’t know a bit about it, even if its just for yourself. I don’t like getting sunburn, especially as its annoying, but it wasn’t until I had a wee look at the statistics that I really got a good look at its impact.
And if you or your patients have got a funky mole or weird patch of skin, get it checked out.
To finish off, here’s my favourite ZDogg getting his moles checked (will probably contain swearing).
Cancer Research: https://www.cancerresearchuk.org/about-cancer/skin-cancer
British Association of Dermatologists: http://www.bad.org.uk/for-the-public/skin-cancer
American Cancer Society (2017) What Is Ultraviolet (UV) Radiation? Available at: https://www.cancer.org/cancer/skin-cancer/prevention-and-early-detection/what-is-uv-radiation.html (Accessed: 21 April 2019).
British Association of Dermatologists (2019) Sunscreen Fact Sheet. Available at: http://www.bad.org.uk/for-the-public/skin-cancer/sunscreen-fact-sheet (Accessed: 22 April 2019).
Dale Wilson, B., Moon, S. and Armstrong, F. (2012) ‘Comprehensive review of ultraviolet radiation and the current status on sunscreens.’, The Journal of clinical and aesthetic dermatology, 5(9), pp. 18–23. Available at: http://www.ncbi.nlm.nih.gov/pubmed/23050030 (Accessed: 22 April 2019).
Goodsell, D. S. (2001) ‘The molecular perspective: ultraviolet light and pyrimidine dimers.’, The oncologist, 6(3), pp. 298–9. doi: 10.1634/THEONCOLOGIST.6-3-298.
Guerra, K. C. and Crane, J. S. (2019) Sunburn, StatPearls. StatPearls Publishing. Available at: http://www.ncbi.nlm.nih.gov/pubmed/30521258 (Accessed: 21 April 2019).
Holman, D. M., Ding, H., Guy, G. P., Watson, M., Hartman, A. M. and Perna, F. M. (2018) ‘Prevalence of Sun Protection Use and Sunburn and Association of Demographic and Behaviorial Characteristics With Sunburn Among US Adults’, JAMA Dermatology, 154(5), p. 561. doi: 10.1001/jamadermatol.2018.0028.
Office for National Statistics (2018) Cancer registration statistics. Available at: https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/bulletins/cancerregistrationstatisticsengland/final2016 (Accessed: 22 April 2019).
Rands, C. M., Meader, S., Ponting, C. P. and Lunter, G. (2014) ‘8.2% of the Human Genome Is Constrained: Variation in Rates of Turnover across Functional Element Classes in the Human Lineage’, PLoS Genetics. Edited by M. H. Schierup, 10(7), p. e1004525. doi: 10.1371/journal.pgen.1004525.
Visconti, R., Della Monica, R. and Grieco, D. (2016) ‘Cell cycle checkpoint in cancer: a therapeutically targetable double-edged sword.’, Journal of experimental & clinical cancer research : CR, 35(1), p. 153. doi: 10.1186/s13046-016-0433-9.