Sun protection involves shielding the skin from the damaging effects of solar ultraviolet (UV) radiation. While visible light is seldom a problem, it can exacerbate certain photosensitivity disorders such as porphyrias.
Solar UV radiation can be classified into three types: ultraviolet A (UVA), ultraviolet B (UVB), and ultraviolet C (UVC). UVC, with a wavelength of 100–280 nm, is absorbed by the atmosphere and does not reach the Earth’s surface. UVB, with a wavelength of 290–320 nm, and UVA, with a wavelength of 320–400 nm, both reach the Earth’s surface and contribute to skin aging and the development of skin cancers such as basal cell carcinoma, squamous cell carcinoma, and melanoma. UVB radiation is particularly potent in causing skin reddening and sunburn by damaging the upper epidermal layers of the skin.
Visible light, with a wavelength of 400–750 nm, can also trigger or aggravate certain photodermatoses, including melasma, postinflammatory hyperpigmentation, lichen planus pigmentosus, solar urticaria, and cutaneous porphyrias. Thus, sun protection methods, including the use of sunscreen and sun-protective clothing, are essential in reducing these harmful effects.
The Global Solar Ultraviolet Index is widely used to assess the risk of sunburn. People with photosensitivity and those with lighter skin (Fitzpatrick skin phototypes I–III) are at higher risk and should take particular care.
To effectively safeguard the skin from harmful UV radiation, it is crucial to implement a variety of sun protection methods.
Sunscreens are topical agents applied to the skin to protect against UV radiation (UVR). They are rated by their sun protection factor (SPF), which measures their ability to shield against UVB rays. Products labelled as ‘broad spectrum’ also protect against UVA wavelengths. An SPF 30+ is considered high protection, and an SPF 50+ offers very high protection if applied in sufficient amounts, approximately 35mL for an average adult. Sunscreen should be applied daily if the UV index is 3 or higher and reapplied at least every two hours. However, during winter months in regions far from the equator, sunscreen may not be necessary year-round.
Many sunscreens that protect against UVR do not shield against visible light. For those with photodermatoses triggered by visible light, tinted sunscreens that remain visible on the skin are recommended.
Sun Protective Clothing includes garments made from UV-protective fabric. A UV protection factor (UPF) rating of 30+ is considered good protection. Everyday apparel, particularly tightly woven and darker-colored fabrics, can also provide sun protection. Clothes that cover more skin, such as hats that shade the face and neck, long-sleeved shirts, high collars, long pants, and enclosed shoes, are recommended.
Shade and Sun Avoidance are crucial as sunscreens and protective clothing do not block 100% of UVR. Reducing sun exposure can be achieved by minimizing time outdoors during peak sunshine hours (10 am to 4 pm in summer), seeking shade, using umbrellas, and tinting windows in vehicles and buildings.
Eyewear, such as sunglasses, ski goggles, and UV-filtering prescription glasses, protect the eyes and eyelids from solar UVR exposure, which can lead to eye diseases such as cataracts, photokeratitis, photoretinitis, macular degeneration, and ocular cancers. Close-fitting, wrap-around sunglasses provide the best protection. Sunglass standards, including UV filtering regulations, vary by region but include ANSI Z80.3-2018 in the United States, EN ISO 12312-1 in Europe, and AS/NZS 1067:1:2016 in Australia and New Zealand.
It is crucial to start photoprotection early, as a significant proportion of lifetime UV exposure occurs before the age of 10. Using wide-brimmed hats and sunscreen with less opaque products can offer good photoprotection. Scarves can protect the neck when non-brimmed hats are worn.
Other Photoprotective Agents, such as nicotinamide (a Vitamin B3 derivative), afamelanotide (an alpha-melanocyte-stimulating hormone analogue), and Polypodium leucotomos extract have been found to have photoprotective and anti-photocarcinogenic properties. Research in this area is ongoing, but the aforementioned sun protection methods remain essential.
Vitamin D is important for bone health and calcium homeostasis. Concerns have been raised that protecting the skin against UVB radiation, which is involved in Vitamin D production, could contribute to Vitamin D deficiency. However, real-life use of recreational sunscreen has not shown this to be a significant issue in trials. Oral Vitamin D supplements are available if deficiency is a concern.
Applying a high SPF and broad-spectrum sunscreen daily if the ultraviolet index is 3 or higher is recommended. Reapply sunscreen every two hours, and after swimming or heavy sweating. Avoid sun exposure during peak sunshine hours (10 am to 4 pm in summer) and stay in the shade where possible. Avoid intentional solar tanning. Choose clothing made from tightly woven and darker fabrics, clothes that cover more skin and those with a UPF of 30 or higher. Put on dry clothes after swimming or getting wet, as wet material is often less protective. Be careful to protect your skin and eyes at high altitudes in any season, particularly in the snow, which reflects extra ultraviolet radiation.
Sun protection is a comprehensive strategy involving various methods to shield the skin from harmful UV radiation. By incorporating these practices, individuals can significantly reduce their risk of sunburn, premature aging, and skin cancer.
