Insulin allergy is a well-documented complication of insulin therapy. A 67-year-old man presented with symptoms suggestive of insulin anaphylaxis. In an attempt to allow him to continue insulin therapy, he underwent a desensitization protocol. During the protocol, he again experienced symptoms suggestive of anaphylaxis. An analysis of his case is presented in the context of current literature. All physicians treating patients with insulin should be aware of this serious complication.