Although much less common than photoallergic contact dermatitis, allergic reactions resulting from the combination of ultraviolet light and a systemic medication (rather than a topical agent) do occur. A large number of agents has been associated with this type of allergy, including sulfonamides (antibiotics such as Gantrisin, Septra, and Bactrim); sulfonylureas (oral antidiabetic drugs such as Tolinase and Orinase); thiazide diuretics (such as HydroDIURIL); quinidine (a heart rhythm regulating drug such as Quinaglute); phenothiazines (such as Thorazine); oral contraceptives; griseofulvin (antifungal agents such as Fulvicin and Gris-Peg); several antihistamines; and piroxicam (Feldene).

Reddish flat-topped bumps and eczema are the most common types of skin eruptions seen in this condition. In general, photoallergic systemic reactions are of the delayed allergy type and thus begin twenty-four to forty-eight hours after UV exposure.

The diagnosis of photoallergic drug reaction is usually made from the history and clinical picture. Occasionally, phototesting may also be helpful in confirming the diagnosis.

Prevention and treatment require either discontinuing the offending medication or avoiding sun exposure. Unfortunately, depending on the particular drug involved, in some cases it may take as long as three to four months for the drug to clear the body and for the symptoms to disappear completely. Of course, when a particular drug is essential for the treatment of a serious medical condition and no equivalent substitution is available, sun avoidance becomes the only alternative. Specific treatment measures are the same as those for photocontact allergy.