Photosensitivity
Types and Mechanisms
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Two types include phototoxic eruptions and photoallergic eruptions.
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Phototoxic eruptions are due to absorption of UV light (usually UVA) by the drug, which causes a release of energy and damage to cells. Looks like a bad sunburn, which may blister.
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Photoallergic eruptions are a lymphocyte-mediated reaction caused by exposure to UVA, which converts the drug to an immunologically active compound that activates lymphocytes, causing an eczematous reaction in a photodistribution.
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Both types can be caused by phenothiazines, chlorpromazine, sulfa, and NSAIDS, although phototoxic reactions are more common with these agents.
Phototoxic eruption Phototoxic eruptions often appear as exaggerated sunburns. Courtesy of Andrew Samel, MD.
