[Cutaneous allergic accidents caused by insulin. Current aspects apropos of 2 cases]

Current data concerning cutaneous allergy to insulin may be illustrated by the two cases reported here. One was a woman with gestational diabetes; she was treated with bovine insulin and developed generalized urticaria which subsided after switching to human insulin. The other was a woman who had pruritus localized to the site of injection with every type of insulin and in whom laboratory examinations showed an increase of specific IgE. Immunological reactions have been described since the time when exogenous insulin was introduced as a treatment of diabetes. The wide use of purified human insulin has considerably reduced their incidence but benign local and immediate systemic reactions are still being reported, their estimated frequency varying from 10 p. 100 to 50 p. 100 of the patients treated. In reality, allergy to insulin itself is extremely rare compared with allergic reactions to preservatives, such as metacresol, additives (protamine and zinc and contaminants present in insulin preparations: desamido-insulin. True allergic reactions to insulin may be localized or generalized and biphasic, and in most cases they are IgE-mediated. Some late local reactions, as well as atrophy, can be ascribed to delayed hypersensitivity. Treatment includes: (i) change in the type of insulin used; (ii) systemic or topical corticosteroid therapy; (iii) antihistamines and aspirin, and (iv) desensitization. The allergic complications of insulin therapy are benign; they usually do not require any particular treatment and often spontaneously regress.