BACKGROUND AND OBJECTIVE: Allergic reactions to insulin, though rare, can have serious consequences in children with type I diabetes mellitus. We report a case of insulin allergy in a 5-year-old child in whom insulin desensitization was accomplished using an insulin pump. METHODS AND RESULTS: A 5-year-old girl with insulin-dependent diabetes mellitus (IDDM) developed progressive reactions to insulin and was found to have positive intradermal skin tests to regular and NPH insulin. Addition of oral antihistamine and co-administration of subcutaneous dexamethasone along with the insulin failed to control her symptoms. The patient was therefore hospitalized and desensitized to insulin using an insulin pump and insulin lispro. CONCLUSION: An insulin pump can be used for insulin desensitization in selected children. The slow constant infusion rate provided by the pump may be an ideal means of achieving insulin desensitization. In addition, insulin lispro, a synthetic insulin analog, should be considered for use in insulin-allergic individuals.