Sun Protection

Sun protection refers to the measures taken to shield the skin from the harmful effects of solar ultraviolet (UV) radiation. While visible light is generally less harmful, it can worsen certain photosensitivity disorders such as porphyrias.

Solar UV radiation is classified into three types: ultraviolet A (UVA), ultraviolet B (UVB), and ultraviolet C (UVC). UVC, with wavelengths between 100 to 280 nm, is absorbed by the atmosphere and does not reach the Earth's surface. UVB (290 to 320 nm) and UVA (320 to 400 nm) penetrate the atmosphere and contribute to skin aging and the development of skin cancers such as basal cell carcinoma, squamous cell carcinoma, and melanoma. UVB is particularly effective at causing skin reddening and sunburn by damaging the upper epidermal layers, while UVA penetrates deeper and accelerates photoaging.

Visible light, with wavelengths of 400 to 750 nm, can also trigger or worsen certain photodermatoses, including melasma, postinflammatory hyperpigmentation, lichen planus pigmentosus, solar urticaria, and cutaneous porphyrias. For this reason, sun protection measures such as sunscreen use, sun-protective clothing, and limiting sun exposure are essential.

The Global Solar Ultraviolet Index is widely used to assess sunburn risk. Individuals with photosensitivity or lighter skin tones (Fitzpatrick skin phototypes I to III) are at greater risk and should take extra precautions.

Sunscreens are topical agents that protect the skin from UV radiation. They are rated by their sun protection factor (SPF), which measures protection against UVB. Products labelled "broad spectrum" also protect against UVA wavelengths. SPF 30+ is considered high protection, and SPF 50+ provides very high protection when applied in sufficient quantities, approximately 35 mL for an average adult. Sunscreen should be applied daily when the UV index is 3 or higher, and reapplied every two hours or after swimming or sweating. In regions far from the equator, sunscreen may not be needed year-round during winter months. Most sunscreens do not block visible light; for individuals with light-induced skin conditions, tinted sunscreens that remain visible on the skin are recommended.

Sun-protective clothing, including garments with a UV protection factor (UPF) of 30 or higher, offers an effective physical barrier. Tightly woven, dark-coloured fabrics provide the best coverage. Wide-brimmed hats, long-sleeved shirts, high collars, long trousers, and enclosed footwear are recommended.

Shade and sun avoidance remain important, as neither clothing nor sunscreen blocks 100% of UV radiation. Limiting outdoor activities during peak sun hours (10 am to 4 pm in summer), seeking shade, using umbrellas, and tinting windows in vehicles and buildings all help reduce exposure.

Eye protection is also critical. Sunglasses, ski goggles, or UV-filtering prescription glasses prevent damage to the eyes and eyelids from UV exposure, reducing the risk of conditions such as cataracts, photokeratitis, macular degeneration, and ocular cancers. Wrap-around designs offer optimal protection, and compliance with regional safety standards is recommended.

Photoprotection should begin early in life, as a substantial portion of lifetime UV exposure occurs before age 10. Scarves, hats, and less opaque sunscreens can help protect children's skin without hindering daily activities.

Certain agents, including nicotinamide (a vitamin B3 derivative), afamelanotide (an alpha-melanocyte-stimulating hormone analogue), and Polypodium leucotomos extract, have shown additional photoprotective and anti-photocarcinogenic effects, though research continues in this area.

While UVB exposure is important for vitamin D production, routine sunscreen use in real-life conditions has not been shown to cause significant deficiency. If needed, vitamin D can be obtained through diet or supplementation.

A comprehensive sun protection strategy combines multiple measures: applying broad-spectrum sunscreen of SPF 30 or higher daily when the UV index is 3 or higher, reapplying regularly, wearing protective clothing, avoiding peak sun hours, seeking shade, and using proper eyewear. These practices significantly reduce the risk of sunburn, photoaging, and skin cancer.