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Allergy Shots (cont.)

How Do Allergy Shots Work?

Immunotherapy does not treat symptoms; it treats the immune system, the source of all allergic reactions. Although the exact details of how allergy shots work is unknown, we do know the general way they affect the immune system.

An allergic reaction occurs when the body is exposed to an external substance (the antigen) that the immune system interprets as a foreign invader. In allergic individuals, the immune system then makes an unusual (allergic) response that harms the body.

  • The white blood cells produce an antibody to the antigen called immunoglobulin E, or IgE. This is called sensitization.
  • When the antibody comes in contact with the antigen, it promotes release of certain chemicals called mediators into affected tissues. Histamine is an example of a mediator.
  • It is the effects of mediators on organs and cells that cause the symptoms of allergic reactions.
  • This overreaction to a harmless substance is often called a hypersensitivity reaction.
Allergy shots desensitize you by turning down this immune response to the antigen. As a result of immunotherapy, the white blood cells no longer respond as strongly to the antigen, and less production of the immunoglobulin E antibody to this antigen occurs. So, when you are exposed to this antigen, less severe allergic reactions occur in affected areas like the eyes, nasal mucosal surfaces, and the bronchial airways.

Are Allergy Shots Right For You?

If you are interested in finding out whether allergy shots might work for you, talk to an allergist certified by the American Board of Allergy and Immunology.

  • Shots may be right for you if you have very severe symptoms that interfere with your normal activities even though you are taking appropriate medication. For more information on medications, see Understanding Allergy and Hay Fever Medications.
  • They are a good option for people who have severe side effects from allergy medications or who cannot take allergy medications at all.
  • Allergy shots are suitable for both children older than 2 years and adults.
  • Allergy shots are generally not given to people with heart problems or severe asthma, to people who take beta-blocker drugs for heart problems, high blood pressure, or glaucoma, or to people who take drugs called monoamine oxidase (MAO) inhibitors.
Allergy shots do not work for all allergens or for all allergic conditions. While they reduce symptoms of allergies such as seasonal allergic rhinitis (hay fever); indoor allergies such as dust and dust mites, molds and mildews, and animal dander; and stinging insect venoms, they are not effective for food or medication allergies at this time. Generally, they are given only for allergens that are bothersome all year long or for significant portions of each year.

Before prescribing shots, your allergist will do a full evaluation.

  • He or she will first go over your medical history and do a brief medical exam.
  • A full series of allergy tests will be performed to confirm your specific allergen(s). Depending on the results, the allergist may go ahead and recommend that you try allergy shots. The specific shots that you receive are based on which allergens you are found to be allergic to.
  • Another purpose of this testing is to make sure you don't have a bad reaction to the very tiny amounts of allergens used in the tests. If you do, you may not be able to take the shots because you might be at higher risk of developing an unlikely, but potentially very severe and even life-threatening, reaction called anaphylaxis.
  • Some people refuse to consider allergy shots because they fear needles. Because the allergen extracts are injected just under the skin, the needles used for immunotherapy are very small, much smaller and finer than the larger needles used for many immunizations and medications. The discomfort associated with these very small needles is minimal. Even most children are able to tolerate the shots very well. Even shot haters can change their minds when their symptoms start to abate.
A final factor in your consideration of allergy shots is your patience. If they are to work properly, the shots must be given in a series over time.
  • The initial series takes at least 6 months, and maintenance therapy should continue for 3-5 years. Trying to speed up the schedule can be dangerous.
  • Most people who have good results begin to see an improvement in their symptoms about 6-12 months after starting the treatment.
  • You will need to continue getting booster (maintenance) shots for some time after completing the first series of shots.
  • While most people are able to stop the shots after 3-5 years without experiencing bothersome symptoms, others have to keep getting shots for longer periods.
  • You need to make a commitment at the beginning to stick with the therapy or you will not see positive results.

Medically Reviewed by a Doctor on 4/4/2016
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