Polymorphous light eruption

Overview
Polymorphous light eruption (PLE), or polymorphic light eruption, is a skin complaint caused by sunlight. Symptoms include skin irritations, which may be itchy or painful, and are sometimes confused with hives. These irritations appear upon exposure to sunlight—sometimes as little as 15 minutes of exposure to the sun can bring onset of the condition—and may last from 1 to 7 days. Generally, PLE resolves without treatment; also, PLE irritations generally leave no scar. The cases of this condition are most common between the spring and autumn months in the northern hemisphere.

Typically, 10-20% of the population are affected. It is more common in females than in males. The condition can affect all ethnic groups and research suggests that 20% of patients have a family history of the complaint. Those suffering from PMLE usually do so by age 30.

The cause of PLE is not yet understood. It is thought to be due to a type IV delayed-type hypersensitivity reaction.

Experimental treatments
As of 2008 a company in Australia named Clinuvel Pharmaceuticals Limited is performing clinical trials with a melanocyte-stimulating hormone named melanotan (which they refer to as CUV1647) for polymorphous light eruption.