Psoriasis therapy. The effect of UV radiation on sensitization to mechlorethamine.

A study was performed to determine the effect of UV-B radiation on the sensitization of patients to topically applied mechlorethamine hydrochloride. Patients with widespread psoriasis were randomized into two groups. One group was given six daily treatments of one minimal erythemal dose (MErD) prior to starting daily applications of a 0.02% mechlorethamine ointment and, thereafter, one MErD weekly; the other group was given daily applications of mechlorethamine but received no UV-B. The improvement of psoriasis was monitored by a severity score system and patients were treated for 30 days, or until contact dermatitis occurred. The addition of UV-B to topical applications of mechlorethamine reduced the incidence of allergic contact dermatitis to mechlorethamine from 64% to 22%. In those sensitized to mechlorethamine, the time required for sensitization to develop was increased from 14 to 23 days by UV-B therapy.