An immune response to a foreign antigen that results in inflammation and organ dysfunction. IgE (immunoglobulin E) antibody tests (blood tests) is used to diagnose an allergy. Allergies can range from life threatening to annoying and include systemic anaphylaxis, throat or larynx swelling, bronchospasm, vasculitis (inflammation of blood vessels), angioedema, hives, eczema, hay fever, rhinitis (nasal congestion), and conjunctivitis (itchy, red eyes).