Abstract: Photoallergic and phototoxic eczema (dermatitis) are classified as exogenous dermatoses, which mean that beside a specific environmental factor (a sensitizer), also the influence of irradiation (ultraviolet light in most cases) is necessary to evoke the symptoms. Therefore, the skin changes are most pronounced on uncovered sites. Numerous drugs may have photosensitising properties, including those intended for longterm therapy (analgesics, antidiabetics, circulation, and neurologic drugs, etc.). For people travelling to the tropics, photosensitising potential of widely-used prophylactic drugs (e.g. antimalarials, antibiotics) may pose a problem. Also, topical drugs and cosmetics, especially perfumes, may be responsible for the development of phototoxic and photoallergic eczema. Paradoxically, active ingredients of sunscreen cosmetics (UV filters) frequently cause photoallergy. The method for the identification of the responsible sensitizer is photopatch test - a modification of patch test, in which additional irradiation of the patch tested skin is done with a minute doses, typically, 5 J/cm2 UVA.
Key words: photoallergy, phototoxicity, photoallergic contact dermatitis, photoallergic systemic contact dermatitis, phototoxic contact dermatitis, phototoxic systemic dermatitis, diagnostics, photopatch test.
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Document created: 1 October 2009, last updated: 4 July 2010.