This test measures the total serum concentration of immunoglobulin E (IgE). IgE is a class of antibodies produced in response to allergens (such as pollen, dust mites, and certain foods) and parasites. IgE binds to receptors on the surface of mast cells and eosinophils, and upon re-exposure to the allergen, its breakdown triggers the release of inflammatory mediators such as histamine, leading to allergy symptoms. An elevated total level usually indicates an allergic or parasitic condition, but it is not specific.