Insulin allergy, either localized or systemic, is a clinical problem that may be encountered by nurse practitioners. Studies have shown that 10 to 37 percent of patients started on animal-source insulin developed an allergic reaction to the agent. With the advent of purified animal-source insulins and of human insulin, this number has decreased, but the problem is unlikely to be completely eradicated. This article presents information about the diagnosis, treatment and management of patients presenting with localized or systemic insulin allergy. A brief discussion of the antigenicity of insulin and the basic immune processes operating in insulin allergy will be included. It is hoped that by acquainting nurse practitioners with the manifestations of insulin allergy and the treatment involved, earlier recognition and intervention will occur. This will help remove an extra burden from a patient who is already trying to adjust to the necessity of daily insulin injections.