ABSTRACT
The term polymorphous light eruption is now restricted to a better delineated group of sun-induced skin rashes. Polymorphous light eruption is an idiopathic, recurrent, acquired abnormal skin reaction to sunlight of delayed onset. It is characterized by a varied appearance of erythematous papules, papulovesicles, plaques, and lesions resembling erythema multiforme lesions on sun-exposed skin areas. The pathogenetic mechanisms of polymorphous light eruption remain unknown. The causative factor that reproducibly induces skin lesions is sunlight. Determination of the action spectrum of polymorphous light eruption by experimental reproduction of skin lesions using artificial radiation sources has led to conflicting results. The histopathologic changes vary with the morphologic type of polymorphous light eruption. The treatment of polymorphous light eruption has to be subdivided into therapy for the acute exacerbation and the prophylactic therapy before expected sun exposure. Drugs are in use for systemic prophylactic intervention in polymorphous light eruption. The mechanisms by which phototherapy induces tolerance to sunlight has not been clarified.
