Changes in Allergic Reactivity

Allergy is characterized by the overproduction of IgE antibodies directed at ubiquitous antigens that activate the immune system after inhalation, ingestion, or penetration through the skin. When antigen is reintroduced, IgE-mediated triggering of high-affinity receptors expressed on the surface of mast cells and basophils initiates the release of mediators involved in the allergic cascade. IgE production depends on the presence of IL-4 released by a subpopulation of allergen-activated T lymphocytes.

Although no data are available on the prevalence of allergic reactions in elderly persons, IgE-mediated hypersensitivity reactions are believed to occur less frequently with age, and allergic symptoms tend to diminish. This belief is supported by the observations that serum IgE production decreases with age because of defective IL-4 production and that reactivity to histamine also decreases significantly.