Chronic urticaria from isophane insulin therapy; sensitivity associated with noninsulin components in commercial preparations.

A young woman with diabetes mellitus developed chronic urticaria after changing from isophane been insulin suspension to isophane beef-pork insulin suspension. She reverted to treatment with her original insulin preparation, but urticaria failed to terminate. While in the hospital, her eruption began each afternoon at the site of insulin injection. Zinc single-peak beef insulin suspension, a purer preparation with different additives than isophane beef insulin, was substituted, and urticaria terminated rapidly. Intradermal skin testing using single-peak (purified) preparations indicated that the patient was sensitive to beef and pork forms of isophane insulin but not to beef and pork forms of zinc insulin. The patient later had a brief recurrence of urticaria following oral erythromycin and tetracycline therapy but did not develop lesions at sites of insulin injection.