dermatologic disorders
Photosensitivity
Polymorphous light eruption
Polymorphous light eruption is a common photosensitive reaction to UV and sometimes visible light. It does not seem to be associated with systemic disease or drugs. A positive family history in some patients suggests a genetic risk factor. Eruptions appear on sun-exposed areas, usually 30 minutes to several hours after exposure; however, sometimes eruptions do not appear for up to several days. Lesions are pruritic, erythematous, and often papular but may be papulovesicular or plaquelike. They are more common among women and people from northern climates when first exposed to spring or summer sun than among those exposed to sun year-round. Lesions often subside within several days to weeks. Diagnosis of polymorphous light eruption is made by history, skin findings, and exclusion of other sun-sensitivity disorders. Diagnosis sometimes requires reproduction of the lesions with phototesting when the patient is not using any potentially photosensitizing drugs. Often, lesions are self-limited and spontaneously improve as summer progresses. Prevention include using a broad-spectrum sunscreen and moderating sun exposure. More severely affected patients may benefit from desensitization in early spring by graduated exposure to UV light with low-dose psoralen plus ultraviolet A (PUVA― see , a natural tropical fern extract, may help prevent polymorphous light eruption, but further studies are needed ( General reference ). 