Immediate or anaphylactic type hypersensitivity to insulin may be detected by in vitro analysis of IgE antibodies against insulin antigenic determinants. A solid phase immunoadsorbent prepared with polystyrene tubes and an IgE anti-IgE matrix provides the method of fixation of serum IgE against radiolabeled insulin. The degree of insulin binding by IgE correlates with the clinical allergic state and declines in parallel with the Prausnitz-Küstner titers of patient's sera. A more rapid decline in IgE-binding capacity of insulin occurred after therapeutic insulin desensitization or continuous insulin therapy. The occurrence of insulin allergy and immunologic insulin resistance in the same patients was associated with the presence of both IgE and IgG antibodies against insulin. The immunoadsorbent system for detection of IgE antibodies against insulin was used to evaluate cross-reactivity of heterologous insulins or insulin fragments with bovine insulin and is applicable to other IgE-mediated systems.