IgE is the class of antibodies produced in the lungs, skin, and mucous membranes. It may protect against parasite invasion, but it is a major factor in allergic reactions. The antigen-specific IgE interacts with mast cells and eosinophils, triggers the release of histamine, leukotrienes and other substances that lead to the itching, sneezing and congestion of allergies - and the life threatening respiratory distress of asthma and anaphylactic shock.