UVB is the cause of sunburn in 85 per cent of cases and is stopped by glass. UVA though isn't stopped by glass and is the main cause of UV-induced malignant change.
Some 65 per cent of UV light reaches the earth between 10am and 2pm and the amount a person is exposed to increases by 4 per cent with every 300m rise in altitude.
Although most sunburn is usually thought of as occurring in the summer it should be remembered that snow and ice reflects 80 per cent of light, compared with 25 per cent from sand.
UV light will penetrate moist skin a lot more easily than dry skin (this may account for the fact that elderly skin is generally more resistant to sunburn).
Many medications have a photosensitising effect on the skin (for example, amiodarone and psoralens) so in cases of sunburn it is always important to take a careful drug history.
Most people are aware of the damage UV can do to skin, but damage to eyes is also very important. There is an increasing incidence of retinal melanomas and
When sunburn has occurred NSAIDs are very useful for their antiprostaglandin effect.
Topical anaesthetics and steroids are best avoided because of the increased risk of sensitisation and subsequent dermatitis.
In severe cases of sunburn high-dose oral steroids may be useful (40-60mg daily for two-three days, except where infection is also present). Interestingly, a dose of 60-80mg prior to sun exposure seems to prevent sunburn in many individuals.
In cases of severe or unexpected sunburn, especially in infants, always consider other underlying contributory conditions such as porphyria or xeroderma pigmentosa.