Allergy Shots

  • Medical Author: Javed Sheikh, MD
  • Coauthor: Kathryn L Hale, MS, PA-C
  • Medical Editor: Jeffrey Lee Kishiyama, MD
  • Medical Editor: Francisco Talavera, PharmD, PhD
  • Medical Editor: Stephen C Dreskin, MD, PhD

Allergy Shots Facts

Allergy shots are usually administered over three to five years with the aim of deadening the body's immune response to common allergens, thus reducing symptoms and medications.
Allergy shots are usually administered over three to five years with the aim of deadening the body's immune response to common allergens, thus reducing symptoms and medications.
  • Some allergens are impossible to avoid. You cannot live a normal life and completely avoid pollen, dust mites, mold spores, and certain other common triggers of allergic reactions.
  • 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.

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.

What Does the Allergist Do?

Before starting immunotherapy, the allergist will take a complete medical history.

  • Be sure to tell him or her about every medication you take, prescription and nonprescription, even those you take only occasionally.
  • Report any vitamins, dietary supplements, herbal products, and other alternative therapies you take.
  • Also report every allergy you know of.
  • If you are a woman, it is essential that you tell your allergist if you are pregnant or have any plans to become pregnant in the foreseeable future. In this case, allergy shots might be better suited for another time. Based on your particular situation, the allergist will tell you your options for treatment of your allergies during pregnancy. In certain situations, allergy shots can be continued during pregnancy, if it is determined that the potential benefits outweigh the risk of an unlikely, but potentially severe, reaction to one of the shots.
The allergist will prepare a schedule for your allergy shots. It is extremely important that you adhere to this schedule.
  • At first you will get the shots often, once or twice a week.
  • After about 6-12 months, you will start maintenance therapy, which means a shot about every month or so.
  • Most people continue to take maintenance therapy for 3-5 years.
The allergist will also keep track of your symptoms to see how well the shots are working for you. The only reason to have further skin testing is if the allergy shots are not working and there is concern that you may have developed more allergies.

What Will Allergy Shots Do For Me?

Immunotherapy, if properly managed, can significantly reduce allergy symptoms. In some people, it greatly reduces the need for allergy medication.

  • These effects become noticeable 6-12 months after starting the therapy.
  • Most people notice continued gradual improvement over the next 2-4 years.
  • By years 3-5, most people are desensitized to their allergen or allergens. Many can stop immunotherapy at that point.

There are several things you can do to increase the success of the therapy:

  • Make a commitment to follow your allergist's recommendations to the letter.
  • Follow through with the entire course of treatment recommended. If you stop half way through, the treatment will not work.
  • Continue to avoid the allergens as much as possible. Just because you complete a course of immunotherapy for your allergy to pet dander doesn't mean you can now go out and get a cat. Immunotherapy is much less likely to work if you do not continue to avoid your allergens.

Do Allergy Shots Have Side Effects?

Generally, allergy shots are safe, with minimal side effects. There are no long-term complications associated with this form of therapy, but there is a small risk of allergic reactions immediately following the injection. These allergic reactions can be severe (see below). Typically, allergy shots may cause slight swelling or redness at the injection site. These reactions can occur immediately after the injection and/or can occur several hours later. This mild allergic reaction is usually harmless and goes away within 24 hours.

The shots may also cause symptoms similar to the allergy symptoms you experience: itchy, stuffy nose; itchy, watery eyes; sneezing. In very rare cases, these symptoms become very severe and are accompanied by other symptoms, including the following:

  • Difficulty breathing or wheezing
  • Chest or throat tightness
  • Rapid or irregular heart beat
  • Dizziness or light-headedness
  • Loss of consciousness
  • Death
This type of very severe allergic reaction is known as anaphylaxis.
  • It is a very uncommon reaction to an allergy shot, but it is dangerous, even life threatening.
  • This is less likely to happen if you follow the schedule of shots recommended by your allergist and observe the technician administering the shot. Be sure you are receiving the correct dose of the correct extract.
  • The dizziness, light-headedness, and loss of consciousness are due to dangerously low blood pressure, usually called "shock." These symptoms occur when the brain is not receiving enough blood.
  • Anaphylactic shock is a medical emergency.
Such severe reactions usually begin within 20-30 minutes after receiving the shots. For this reason, most allergists require that you wait in the office for 20-30 minutes after your shots to be monitored. If you should experience these symptoms at any time, tell the allergist or other medical professional right away.
  • If you have already left the allergist's office, and are having a severe reaction, go directly to the nearest hospital emergency department. If you already have and Epi-pen, use it. If you have an antihistamine such as Benadryl, take it regardless, go to the nearest hospital emergency room or urgent care center as soon as possible.
  • Do not attempt to drive yourself. If no one is available to drive you immediately, call 911 for emergency transport.

"Subcutaneous immunotherapy for allergic disease: Indications and efficacy"