Since the introduction of specific immunologic measures for the treatment or prevention of poison ivy dermatitis, the more than one hundred year old controversy as to their usefulness has continued, and no decisive answer is at hand even today. It appears that desensitization was first suggested by the American Indian practice of chewing the leaves of the poison ivy plant. Dakin,1 in 1829, was probably the first medical authority to report the beneficial effects of specific desensitization. He stated that laborers and other persons chewed the leaves to gain immunity and that physicians advised that the forbidden fruit be eaten. Alumbaugh,2 in 1898, half filled a vial with the buds or leaves of Rhus toxicodendron, poured into the flask enough alcohol or whisky to fill it completely and allowed this to stand for one day. He then made a third decimal dilution. Twenty drops of this were placed