Photoxic dermatitis In phototoxic reactivity, no immunologic mechanism is involved, and the patient reacts as anyone would to a primary irritant. Phototoxic drugs and chemicals include some dyes, coal tar derivatives, and psoralens. Drugs that may cause a phototoxic reaction include the sulfonamides, tetracyclines, and thiazides. Pictured in Fig. 11-6 is a teenager who developed erythema on the backs of his hands from sun exposure while taking doxycycline for his acne.