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doxycycline, phototoxicity, rash
Commonly used in clinical practice, doxycycline has been known to produce a cutaneous phototoxic reaction in combination with sunlight. Several mechanisms have been proposed to contribute to its pathogenesis such as UVA oxidation of cellular components, the formation of photoproducts, and altered melanogenesis. We describe a case of a phototoxic rash in a patient taking doxycycline 100 mg daily for the treatment of rosacea. We present several photos of the rash from erythema to desquamation several weeks later. The clinical presentation of a doxycycline-induced phototoxic rash varies from a sunburn like sensation to diffuse erythematous plaques on sun exposed areas. Treatment involves discontinuing the drug and providing symptomatic relief. Although sunscreen may prevent a doxycycline-induced phototoxic reaction, it is important to educate the patient to use a sunscreen with protection in the 340-400 nm range in which phototoxic reactions are thought to occur. As doxycycline-induced phototoxicity is poorly understood, it may be best to advise the patient to avoid sun exposure altogether while taking the drug.
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