Polymorphous light eruption, also known as polymorphic light eruption, is an itchy rash caused by sun exposure in people who have developed a sensitivity to sunlight (photosensitivity). The rash usually appears as red, tiny bumps or slightly raised patches of skin.
Polymorphous light eruption occurs most often during spring and early summer when a person's exposure to sunlight increases. Repeat episodes are less likely as the summer progresses, but polymorphous light eruption often recurs each year after the first incident.
Although polymorphous light eruption usually goes away on its own without treatment, medications may be needed to treat severe or persistent cases. Measures to protect the skin from sun exposure or light therapy may help prevent recurring episodes of polymorphous light eruption.