title: Irritant potential of dithranol.
abstract: The minimal irritation dose (MID) for dithranol in 5% salicylic acid vaseline was determined by open patch testing. From the MID, the irritation dose 50 (ID50) was evaluated. It was 0.057% in 100 controls and 0.046% in 100 psoriatic patients, which is not statistically different due to the great differences between individuals. 20 other patients claimed a dithranol hyperreactivity in their history. Only 13 of them, however, showed a decrease in the MID, which was between 0.01 and 0.02% (means = 0.014%), i.e. outside the confidence interval found in the 100 psoriatic patients. 8 of these 13 reacted with blister formation after exposure to 0.1-0.16% dithranol. An allergic contact dermatitis was excluded as the cause of the hyperreactivity. The tolerance to increasing dithranol concentrations after beginning with the MID up to clearance of the lesions, as well as the predominance of granulocytes as compared to lymphocytes in blisters due to dithranol testing, suggest an irritant inflammatory mechanism. In such hyperreactive cases therapy should be started with the MID established in the open patch test.
mesh_terms: D000875:Anthralin / Q000009:adverse effects / Q000627:therapeutic use / Q000633:toxicity*; D001768:Blister / Q000473:pathology; D003877:Dermatitis, Contact / Q000175:diagnosis / Q000209:etiology; D004305:Dose-Response Relationship, Drug; D004344:Drug Incompatibility; D004890:Erythema / Q000139:chemically induced; D006098:Granulocytes / Q000473:pathology; D006801:Humans; D007509:Irritants; D011565:Psoriasis / Q000150:complications / Q000188:drug therapy; D012882:Skin Tests / Q000379:methods
chemical_list: D007509:Irritants; D000875:Anthralin