INCIDENCE OF INSULIN ALLERGY INSULIN allergy, the antigenic response to the insulin protein, is a rare but important occurrence in diabetic management. The incidence of allergic reactions to insulin varies widely in the reports in the literature. Some observers considered mild local reactions as allergic manifestations. Others were found to exclude all local reactions regardless of severity and to designate as allergic only those patients for whom insulin therapy had to be discontinued. Hence such wide variations as Grafe's 1 0.15 per cent, Collens' 2 7.3 per cent and Allan and Scherer's 3 11.7 per cent were reported. Of persons sensitive to insulin, Allan and Scherer estimate that from 98 to 99 per cent will show a reaction limited to the site of injection while only 1 or 2 per cent will exhibit general or systemic manifestations. Thus, approximately one in a thousand using insulin will have a generalized reaction. Mild local reactions