Failure to Induce Immune Tolerance to Nitrogen Mustard. Intravenous Administration Preceding Topical use in Patients with Psoriasis

The nitrogen mustard mechlorethamine (NH₂) is a potent contact allergen, sensitizing up to 75% of those exposed. An attempt was made to prevent allergic contact sensitization, i.e. to induce specific immunologic tolerance, in 9 patients who were to be treated topically with NH₂ for widespread and persistent psoriasis. Fourteen and 7 days before the first topical application of NH₂, they were given intravenous injections of 3 mg NH₂. Topical treatment with NH₂ was repeated weekly for 8 to 10 weeks in 4 patients and daily for about 4 weeks in 5 patients. Two of the 9 patients became contact allergic to NH₂. Despite the apparent failure to induce tolerance, further trials in a larger series of patients and trials with different “tolerogenic” schedules and different topical treatment schedules are warranted.