Many allergy sufferers use medications such as antihistamines and steroid nasal sprays to suppress their symptoms, and these medications are very effective in most. For people with very severe symptoms, and those who cannot take allergy medications, immunotherapy is an alternative.



Immunotherapy is the name for a treatment used by allergy specialists (allergists) to reduce sensitivity to allergens. This therapy is particularly useful for people with allergic rhinitis (sometimes called hay fever). Immunotherapy involves a series of injections (shots) given regularly for several years. In the past, this was called a serum, but this is an incorrect name.

Most allergists now call this mixture an allergy extract. The first shots contain very tiny amounts of the antigen or antigens to which you are allergic. With progressively increasing dosages over time, your body will adjust to the antigen and become less sensitive to it. This process is called desensitization.

Immunotherapy is the only available treatment that can modify the natural course of the allergic disease. This means that a 3- to 5-year regimen of injections may result in long-term benefits that extend well beyond the completion of the regimen. Immunotherapy does not work for everyone and is only partly effective in some people, but it offers allergy sufferers the chance of eventually stopping medication or reducing the amount they have to take.

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.