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All About Allergy Shots

Subcutaneous Immunotherapy – Everything You Need to Know

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Updated January 22, 2013

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

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.

Find out more about how allergy shots work.

Allergy Shot Basics: The Nuts and Bolts

The method of immunotherapy consists of starting at a small dose that will not cause an allergic reaction, with slowly advancing the dosage until the person becomes tolerant to large amounts of the extract. These injections are initially given once to twice a week until a maintenance, or constant dose, is achieved. This usually takes approximately 3 to 6 months. Once the maintenance dosage is reached, the allergic symptoms are largely resolved in most patients. Thereafter, the injections are given every two to four weeks. Therapy is continued for 3 to 5 years total, after which the patient continues to get benefit for another 5 to 10 years or longer, even after the shots are stopped. If the shots are stopped prior to a total of 3 years, the allergic symptoms typically return more quickly.

Potential Side Effects of Allergy Shots

The risks of immunotherapy consist of the possibility of experiencing an allergic reaction to the allergy shot. Most allergic reactions consist only of mild to moderate swelling and itching at the site of the injection. These reactions occur frequently, but rarely require any change in treatment. A large swelling may require an adjustment of the immunotherapy dosage or a change in the frequency and amount of the shots. Less commonly patients experience whole-body allergic reactions, sometimes called anaphylaxis. Most of these reactions are mild and consist of itching of the skin, nasal allergy symptoms and worsening asthma. Others are more severe and can present as cough, chest tightness, wheezing, throat tightness, shock and rarely can be life threatening. For this reason, it is required that patients remain in the physician’s office for 30 minutes after the injection, since most serious reactions occur during this time. These reactions are typically easily reversed with medicines such as injectable epinephrine and antihistamines.

Rush Immunotherapy: Getting Better Faster

Rush immunotherapy involves giving a person multiple allergy shots over a period of many hours to days, achieving a maintenance dose (or near-maintenance dose) in a very short amount of time. After the initial period of rush immunotherapy, a person is able to come into the allergist’s office typically only once a week for the next many weeks, then even less often. People undergoing rush immunotherapy also achieve benefit from allergy shots much faster, usually within a few weeks. Unfortunately, rush immunotherapy results in allergic reactions in a large percentage of people, so various medications (such as antihistamines and corticosteroids) are often given in order to prevent or minimize these reactions. A person undergoing rush immunotherapy should be prepared to spend at least a couple of days in the allergist’s office, receiving many allergy shots over this time.

Allergy Shots for Children

In general, allergy shots are safe and effective therapies, even when administered to children. However, this therapy is not usually recommended in children less than 5 years of age. This is not a hard and fast rule; but is a useful cutoff point to determine when a child is mature enough to communicate symptoms of a reaction to the allergy shots, which may require treatment. Maturity is much more important than age, and children mature at different ages. A child is mature enough to receive allergy shots when the child can come into the doctor’s office knowing they will receive an injection and not cry or fight the process. The child also needs to be able to communicate with their parent or with the medical staff if they are having symptoms of anaphylaxis as a result of the allergy shots.

Some children are mature enough to understand the process of allergy shots at age 5 or 6, while other children may not be mature enough until 8 or 9 years of age. Still other children won’t be mature enough until 11 or 12. A good test is to see how the child did with allergy skin testing – if the child did not fight or cry with this procedure, there is a good chance that they are ready for allergy shots.

Read more: Do allergy shots hurt?

Allergy Shots During Pregnancy

Allergy shots can be continued during pregnancy, but it is not recommended to start this treatment while pregnant. Typically, the dose of the allergy shots is not increased during pregnancy, and many allergists decrease the dose. Some allergists feel that allergy shots should be stopped during pregnancy, given the risk of anaphylaxis and possible danger to the fetus as a result. Other than anaphylaxis, no data shows that the allergy shots themselves are actually harmful to the fetus. A discussion of the risks and benefits of continuing allergy shots during pregnancy should be had between the patient and allergist, with input from the patient’s obstetrician, before deciding on a treatment regimen.

Allergy Shots in the Elderly

There are specific concerns with the safety of allergy shots in the elderly (particularly people 65 years of age and older), especially if the person has other medical problems or is taking certain medications. Older people are more likely to have high blood pressure, heart problems, and a history of blood clots or strokes. Allergy shots should be used with extreme caution in people with these medical problems. The treatment for anaphylaxis, epinephrine injections, may also cause additional problems in older patients with any of the above medical problems.

In addition to certain medical problems, older patients are more likely to be taking medications that place them at a higher risk of reactions from allergy shots. Beta-blockers are a class of medication used to treat high blood pressure, hearts, and are frequently taken in someone who has had a heart attack. These medications can worsen anaphylaxis and make reactions to allergy shots more difficult to treat, and therefore allergy shots should not be given to someone who requires a beta-blocker medication.

You’ve learned all about allergy shots, now learn more about allergy drops (sublingual immunotherapy).

Source:

Cox L, Nelson H, Lockey R. Allergen Immunotherapy: A Practice Parameter Third Update. J Allergy Clin Immunol. 2011 Jan;127(1 Suppl):S1-55.

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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