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realthough I am writing this in the pouring rain, it is now summer, and we have seen a lot of beautiful weather. It is very tempting to go out and enjoy the sun, but it is also important to make sure you are protected – go buy some sunscreen. As someone with porphyria, I am well aware of some of the dangers of sunlight – but what are they? How does sunscreen actually work to protect us and what type should we use?
Sunlight is made up of packets of energy called photons. It is the photons of ultraviolet (UV) light, which have a shorter wavelength than visible light, that can damage the skin. When we think of this light, we divide it into two categories – UVA (in the 320-400 nanometer wavelength range) and UVB (280-320 wavelength range). There is also a third wavelength of radiation, UVC, but it is not able to enter our atmosphere and therefore is not harmful to our skin.
Our skin contains molecules that are perfectly structured to absorb the energy of UVA and UVB photons, putting them in an energetically excited state and causing them to undergo chemical reactions. In our skin, this leads to biological consequences, one of which is tanning – we tan due to the production of extra melanin pigment induced by UVA rays. UVA penetrates deeper into the skin than UVB, destroying a structural protein called collagen – as it breaks down, our skin loses its elasticity and smoothness, resulting in wrinkles. UVB rays are the cause of sunburn.
DNA itself can also absorb both UVA and UVB rays, causing mutations which, if left unrepaired, can lead to non-melanoma or melanoma skin cancers. Other molecules in the skin transmit absorbed UV energy to reactive oxygen species and free radicals, and the resulting oxidative stress can overload the skin’s integrated antioxidant network, causing cellular damage. Photo damage builds up over a lifetime from repeated exposure, and no matter how much melanin we have in our skin, we can develop UV-induced skin cancer.
The best way to protect yourself is to avoid overexposure to UV rays, and that’s where sunscreen comes in. Sunscreen uses UV filters, which are molecules specially designed to help reduce the amount of UV rays that pass through the skin’s surface. A film forms a protective barrier and absorbs or reflects UV photons before they can be absorbed by our DNA and other molecules. They can be classified as both organic (chemical) and inorganic (physical), and many types of sunscreens combine the two compounds to provide a broad spectrum of protection.
The best way to protect yourself is to avoid overexposure to UV rays, and that’s where sunscreen comes in.
In the UK, many brands of sunscreen have both a sun protection factor (SPF) and a five-star rating. SPF refers to the time it takes for UVB rays to redden the skin with sunscreen, compared to without, and it is recommended that you find a brand with at least a 15 rating. SPF 15 blocks around 93% of UVB rays, and that goes up to 98% at SPF 50. Labeled sunscreens block broad-spectrum UVA and UVB rays, but there is currently no standard listing for UVA blocking power. A star rating, on the other hand, refers to the percentage of UVA absorbed relative to the amount of UVB absorbed – the optimal sunscreen is a high SPF and a high star solution.
Once you’ve purchased your sunscreen, how do you use it? You should apply it to your body 15 to 30 minutes before going out, and reapply every two hours regardless of the SPF level. It should also be reapplied after swimming, wiping or sweating. It is also advisable to apply sunscreen even on a cloudy or cool day, regardless of the season – sand, water and snow can all reflect sunlight, and the effects of UV radiation can occur as whether or not you felt a burn.
As always, when the weather is nice, it’s important to take steps to protect yourself and your body. Get outside and enjoy the beautiful sun, but be sure to take this advice to heart – it will pay off in the long run, I promise.
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