Allergies result from an overreaction of the immune system to foreign substances. An allergy develops when the body is exposed to a substance that prompts the initiation of an immune response. This response involves the production of antibodies, called immunoglobulins (Igs), which are directed against proteins of the foreign substance, called allergens or antigens. While there are five classes of immunoglobulins, it is IgE that is typically involved in allergic reactions. When an allergy-prone individual is exposed to a specific antigen, B-cells producean IgE that recognizes only that antigen. This antigen-specific IgE then binds to receptors on specific cells that reside in tissue (mast cells) or circulate in the blood (basophils). Upon re-exposure to the same antigen, the antigen-specific IgE binds to membrane receptors on tissue mast cells and blood basophils and then releases a series of chemicals (histamine, leukotrienes, cytokines and proteases) that regulate the allergic reaction. While the allergic reaction begins immediately, signs and symptoms of the reaction may occur within seconds or minutes (immediate hypersensitivity), may be delayed for several hours (delayed hypersensitivity), or may involve both early- and late-phase reactions.
Allergy tests are performed to verify or exclude the presence of IgE-mediated hypersensitivity and to identify the causative allergen(s). Testing may involve in vivo procedures, which determine the presence of specific IgE by administering an IgE-specific allergen into, on or near the patient and monitoring the patient’s physiological response(s). Allergy tests may also be in vitro procedures that determine the presence of specific IgE or elevated total IgE by analyzing patient serum.
The allergy testing methods and recommendations detailed below are based primarily on practice parameters and recommendations from the American Academy of Allergy, Asthma, and Immunology (AAAAI) and the American Academy of Otolaryngic Allergy (AAOA).