A small number of people develop rashes after exposure to sunlight. There are a number of syndromes in which exposure to ultraviolet light, either outdoors or in a tanning salon, results in a rash. Some patients only experience rashes from sun exposure when they are taking an oral medication, such as an antibiotic.The rash often appears as a deep, red sunburn which persists for several days after the sun exposure and may itch or burn. Some patients experience a delayed reaction to sunlight that takes the form of eczema, a condition called polymorphic light eruption.
In these patients, some combination of redness, bumps, blistering, and itching typically occurs many hours after sun exposure and may persist for up to a week. Other patients will develop hives within 30 minutes of being in direct sun, which is referred to as solar hives or urticaria. These skin lesions appear like other forms of hives, with itchy welts that resolve within 30 to 60 minutes. If you have some form of sun sensitivity, you can reduce your risk of a reaction by limiting your time in the sun. One important step is to wear sunglasses, long-sleeved shirts, and wide-brimmed hats while you are outside.
If you have solar urticaria, your doctor may recommend the use of oral antihistamines to prevent or reduce a reaction as well as the use of sunscreen. However, sun-screens do not block ultraviolet rays completely, so you may still experience a skin reaction.