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Allergy Shots (Allergen Immunotherapy)

What Is It?

Allergic symptoms ? the familiar sneezing, runny nose, itchy eyes or asthma attacks ? are caused by the body's reaction to a substance (allergen) that is inhaled, touched or eaten. You also can develop a rash from a substance you touch or get stomach upset, hives or difficulty breathing from something you eat. These allergens usually are harmless, but in an allergic person, the body responds to the allergen as it would respond to a dangerous invader, such as bacteria or a virus. The immune system recognizes the substance as foreign and activates an army of antibodies to eliminate the invader. The antibodies bind with the allergen and stimulate the release of chemicals, such as histamine, that cause allergy symptoms.

Standard treatment for mild to moderate allergies involves avoiding the allergen that causes the allergic reaction and taking over-the-counter or prescription medications. But when these options are not enough to get rid of symptoms, if allergies are severe or if you have significant side effects from taking your prescription medications, allergen immunotherapy may be recommended.

What It's Used For

Allergen immunotherapy, also known as allergy shots, is a way of desensitizing the body so that it stops reacting so strongly to certain allergens. Tiny amounts of the offending substance are injected under the skin to stimulate the immune system a little each time. Gradually, over weeks and months, the amount of allergen is increased. It's not clear how allergy shots work, but it is believed the treatment stimulates a different type of antibody that binds to the allergen and prevents the allergic reaction. This treatment does not provide short-term relief, but it can be a long-term solution when it works. It can take about six months to a year for symptoms to start to subside. When immunotherapy works, it can significantly decrease the severity of symptoms and how often they occur. However, for some people, there may be no or little effect even after a year.

Allergy shots usually are recommended for people with severe allergy symptoms who do not respond to usual medications or have significant side effects from their medications. Other candidates include those who find their lives disrupted by allergies or for whom allergies might become life threatening, such as people who develop asthma attacks or a severe allergic reaction called anaphylaxis. It also can be used to reduce the severity of reactions to insect stings.

Preparation

Before allergy shots can be given, you must have tests to determine which allergens are causing your allergic reactions. These tests include skin or patch testing, and a blood test called a radioallergosorbent test (RAST). The tests are not always accurate, so you can have a positive test with no allergy symptoms or a negative test and still have allergy symptoms.

How It's Done

A small amount of allergen is injected under the skin, usually in the fleshy part of the upper arm. In the beginning, injections usually are given once a week, and the doses of allergen are increased gradually with each injection. The maximum dose, called a maintenance dose, is reached after four to six months. The maintenance dose is given once a week or once every two weeks. After several months, the injection schedule may be reduced to once every three or four weeks. A full course of allergy shots usually takes between three and five years.

Follow-Up

After each injection, you will be asked to remain in the clinic or waiting room for 20 minutes or longer so that any reactions to the injection can be recognized and treated immediately. People receiving allergy shots will be asked to keep to a strict schedule of injections, because missed injections may reduce the benefits and delay the effectiveness of treatment.

Risks

Most people do not have any bad reactions to allergy shots. Sometimes, you may develop swelling, redness or itching at the site of the injection. These mild reactions typically are treated with antihistamines, and your doctor may decide to adjust the dose for the next injection.

On rare occasions, a more severe reaction will occur. In some sensitive people, the allergy shot can cause asthma symptoms, including difficulty breathing, wheezing or coughing. Or, an anaphylactic reaction will cause dizziness, nausea, swelling of the throat that can prevent breathing or tightness of the chest. These reactions usually can be treated in the office, but occasionally, they may require treatment at a hospital.

When To Call A Professional

Call your physician or allergist if you notice any redness or swelling at the site of the injection or if you experience any coughing or wheezing after a recent injection. If you develop difficulty breathing or talking, tightness in the chest, or if your throat is closing, you or someone with you should call your local emergency number.

Additional Info

American Academy of Allergy, Asthma, and Immunology (AAAAI)611 East Wells St.Milwaukee, WI 53202Toll-Free: (800) 822-2762http://www.aaaai.org/

National Institute of Allergy and Infectious Diseases (NIAID) Building 31, Room 7A-5031 Center Drive MSC 2520Bethesda, MD 20892-2520Phone: (301) 496-5717http://www.niaid.nih.gov/

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