Hypersensitivity Desensitization

Desensitization

A long-term form of allergy treatment involving gradual exposure to small doses of allergens over a period of several years. Also known as immunotherapy and allergy shots.

Desensitization is a form of allergy treatment that involves the periodic injection of small amounts of allergens over a period of several years. Allergens such as dust and pollen cause certain people to produce elevated levels of immunoglobulin E (IgE) antibodies, which in turn unleash chemicals called histamines that produce allergic reactions. By introducing allergens into the body in a highly diluted form, desensitization is designed to increase the immune system's tolerance to these substances so that they no longer cause such allergic reactions as asthma, sinus congestion, sneezing, and red, watery eyes. Allergy shots are effective for many of the approximately six million Americans who receive them regularly. However, the desensitization process is long, time-consuming, and expensive and doesn't work for everyone. In addition, it is not recommended for all types of allergies.

Each course of treatment is individually tailored: a person receives injections containing small portions of only those allergens to which he or she has demonstrated sensitivity. The initial doses are extremely low. If tolerated, they are gradually increased until they reach a maintenance level at which they may be continued for years. Children are usually given a shot in the arm once a week and required to remain in the allergist's office for 20-30 minutes afterwards in case of a serious reaction, either local or systemic. Local reactions may be limited to a feeling of warmth at the injection site or they may be more serious, involving pain and swelling. The weekly schedule is typically maintained for a period of four to eight months, after which the shots are given at increasingly longer intervals. The shots are generally continued until allergic symptoms have been absent for about a year and a half. In most cases, it takes three to five years to reach this point.

While desensitization has proven successful in promoting immunization against some allergens—notably tree and grass pollens, dust, ragweed, and molds—it is not recommended for use against food allergies. Because of the long-term effort and expense involved, it is considered appropriate only for moderate to severe allergies and it is usually undertaken only if an allergy doesn't respond to medication. The major types of allergies for which desensitization is recommended are rhinitis (both seasonal and chronic) and asthma. Rhinitis is the inflammation of the mucous membranes that causes a runny nose, sneezing, and nasal irritation. The seasonal variety (also called hay fever) occurs at the same time every year and is a reaction to specific plants (trees and grass in springtime, ragweed in late summer and fall). The chronic variety may be caused by plants but also by dust, food, or other allergens. The more limited the range of allergens, the better desensitization will work. Allergy shots have also proven effective in treating asthma, in which swelling and congestion of the bronchial tubes cause coughing, wheezing, and shortness of breath. Desensitization is not recommended for skin allergies, such as hives and eczema.

Allergic reactions to insect stings have been successfully treated by desensitization to the venom of particular insects. Such treatments have been demonstrated to be almost 100% effective for reactions that are systemic (rather than limited to the location of the sting), involve either the respiratory or cardiovascular system, and include either a decline in blood pressure or obstruction of an airway. In addition, best results are obtained when the patient has tested positive for insect venom either by skin testing or the radioallergosorbent (RAST) blood test. In almost all cases, the injection causes either no reaction or a local reaction limited to redness, swelling, or discomfort at the injection site. Severe systemic reactions, including anaphylactic shock, a potentially fatal constriction of airways and blood vessels, are possible, so it is important to follow the general desensitization precautions by remaining at the doctor's office for at least 20 minutes after the shot.

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Author Info: , Thomson Gale, Detroit, Gale Encyclopedia of Childhood and Adolescence, 1998

This feature is for informational purposes only and should not be used to replace the care and information received from your healthcare provider. Please consult a healthcare professional with any health concerns you may have.