Sun allergy is a term often used to describe a number of conditions in which an itchy red rash occurs on skin that's been exposed to sunlight. The most common form of sun allergy is polymorphic light eruption, also known as sun poisoning.
Some people have a hereditary type of sun allergy, while others develop signs and symptoms only when triggered by another factor — such as certain types of medications or skin exposure to plants such as limes or wild parsnip.
Mild cases of sun allergy may resolve without treatment. More severe cases may require steroid creams or pills. People who have a severe sun allergy may need to take preventative measures and wear sun-protective clothing.