Polymorphous light eruption
Polymorphous light eruption is a rash that occurs due to sensitivity to sunlight (photosensitivity). Within hours of sun exposure — usually in the spring or early summer — you might notice an itchy, red rash in sun-exposed areas. The spots occur most often on the upper chest, neck and the back of the arms.
The rash usually resolves on its own within a few days, although the condition can occur again. In the meantime, limit sun exposure and wear sun-protective clothing and sunscreen. An over-the-counter anti-itch cream, such as hydrocortisone cream, might help ease discomfort. Talk to your doctor if the reaction is severe or painful.