IgE is a class of immunoglobulins that is produced only in mammals. IgE is secreted by mast cells in response to allergens and is important in immunity against parasites. It also is the most important factor in the pathophysiology of anaphylaxis or type I hypersensitivity. The antibody preparation is specific for human IgE when tested against purified human IgA, IgG, IgM, Bence Jones κ, and Bence Jones λ proteins. Identity and purity of the antibody is established by immunoelectrophoresis.