Updated July 29, 2015.
Written or reviewed by a board-certified physician. See About.com's Medical Review Board.
What are Allergy Shots?
Allergy shots, also known as subcutaneous immunotherapy, have been used for over 100 years for the treatment of allergic rhinitis, allergic conjunctivitis, allergic asthma, and more recently for atopic dermatitis (Allergy shots are also used for venom allergy, but not for food allergies). Immunotherapy is the only treatment for allergies that can effectively cure, or at least significantly reduce, the symptoms of allergies.
Allergy shots involve the administration of the substance a person is allergic to (such as pollens, pet dander, molds and dust mites), which would seem to worsen allergy symptoms. When allergens are administered in an injection form under the skin, however, the body treats the allergens more like a vaccine. Therefore, allergic reactions don’t occur and allergic symptoms don’t happen – at least as much as before allergy shots.
How Do Allergy Shots Work?
Allergy shots have been given for about 100 years for the treatment of allergic rhinitis, allergic conjunctivitis, and allergic asthma. While we know that allergy shots are an effective treatment for these allergic diseases, we’ve only recently known how allergy shots work.
Allergy shots involve the administration of exactly what a person is allergic to (such as pollens, pet dander, molds and dust mites), which would seem to worsen allergy symptoms. Symptoms do, in fact, worsen when a person has natural exposure to allergic triggers – meaning when allergens contact mucous membranes (such as the eyes, nose and lungs), mast cells bound with IgE bind to the allergens and release chemicals such as histamine, causing allergic symptoms.
However, when allergens are administered in an injection form, under the skin, the body treats the allergens more like a vaccine. Infection-fighting antibodies, or IgG, are formed against the allergens, which act to “turn off” the body’s production of IgE. When IgE stops being made, mast cells in mucous membranes won’t be activated as easily when natural allergen exposure occurs. Therefore, allergic reactions don’t occur and allergic symptoms don’t happen – at least as much as before allergy shots.
In addition, as a result of allergy shots, the immune system becomes "tolerant" of the allergen, releasing special chemical signals that tell various immune cells to stop reacting abnormally to the allergens. This also results in the decreased production of IgE, and ultimately reduces allergy symptoms.
Best of all, the changes that occur in the immune system as a result of allergy shots last for many years, even after a person stops getting allergy shots. Therefore, the clinical benefit of the reduction or elimination of allergy symptoms can last for many years even after the allergy shots have been stopped.
Source:
American Academy of Allergy, Asthma and Immunology. Allergen Immunotherapy Practice Parameters. Ann Allergy Asthma Immunol. 2003; 90:S1-40.
DISCLAIMER: The information contained in this site is for educational purposes only, and should not be used as a substitute for personal care by a licensed physician. Please see your physician for diagnosis and treatment of any concerning symptoms or medical condition.
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