These IgE antibodies attach themselves to mast cells that are abundant in the respiratory tract, digestive system, and skin and to basophils, cells circulating in the blood. The next time an allergen and its IgE antibodies come together, mast cells and basophils release powerful substances called mediators, among them histamine, that cause the allergic reaction. These mediators are fairly rapidly neutralized by the body. But as long as the allergen is present, histamine and other mediators will continue to be released from mast cells and basophils, and the patient's allergy symptoms will persist. No one knows for sure why some people have allergies while most do not.
Susceptibility seems to be related to a person's capacity to produce IgE antibodies.
Yet only 30 percent to 40 percent of people with allergic rhinitis have high IgE levels, and individuals with low IgE levels can still suffer from hay fever and other allergies. In view of all the grief they cause, you have to wonder if IgE antibodies are good for anything. The answer may well be yes. Studies suggest that several kinds of human parasites provoke the formation of IgE antibodies and are rapidly destroyed by them. Sometimes this can be fairly easy.