Insulin hypersensitivity reactions are rare, but cause significant complexity in the care of patients with diabetes mellitus. A 54-year-old Filipino male with type 2 diabetes mellitus and multiple co-morbidities developed delayed-type hypersensitivity reactions to biphasic isophane human insulin and glargine. Despite good glycemic control on oral hypoglycemic agents, his endocrinologist foresaw the need for future insulin therapy, particularly one basal and one short-acting insulin. Targeted skin tests demonstrated protamine allergy and negative reactions to regular insulin and detemir. Close coordination of care among endocrinologists, allergists, patients and patients' family is needed to optimize glucose control, prevent complications, and minimize the risk of future hypersensitivity reactions.

Key Words: drug hypersensitivity, insulin, diabetes mellitus