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When you get immunotherapy in the form of allergy shots, your allergist or doctor injects small doses of substances that you are allergic to (allergens) under your skin. This helps your body "get used to" the allergen, which can result in fewer or less severe symptoms of allergic rhinitis.
Your allergist will use an extract of grass, weed, or tree pollen; dust mites; moulds; or animal dander for allergy shots. You must first have skin testing to find out which allergen you are allergic to.
Your allergist injects under your skin a solution of salt water (saline) that contains a very small amount of the allergen(s). At first, you get the shot once or twice a week. You gradually receive more of the allergen in the shots.
After about 4 to 6 months of weekly shots, you are usually getting the best amount of allergen in the shot. This is called the maintenance dose. When you reach the maintenance dose, you get the same dose in shots every 2 to 4 weeks for the next 4 to 6 months.
The period between shots is gradually increased to about a month. And the dose usually stays the same each month. After 1 year of maintenance, your allergist will check to see if you have fewer or less severe symptoms. If your allergy symptoms have not changed, you will no longer get the shots. If your symptoms have improved, you may continue to get monthly shots for up to 3 to 5 years.footnote 1
Other ways to get this treatment are called cluster or rush immunotherapy, in which you reach the maintenance dose more quickly.
What To Expect After Treatment
You receive allergy shots in your allergist's office. You will stay in the office for 30 minutes after you get the shots, in case you have a severe reaction (anaphylaxis) to the injected allergens.
Redness and warmth at the shot site are common. But these go away after a short period of time.
Why It Is Done
Allergy shots can reduce your reaction to allergens, which can result in fewer or less severe symptoms. They may also prevent children who have allergic rhinitis from getting asthma.footnote 1 Recommendations on when to get allergy shots vary, but in general you and your doctor may consider them when:
- Allergy symptoms are severe enough that the benefit from the shots outweighs the expense and the time spent getting the shots.
- You are allergic to only a few substances, and they are hard to avoid.
- Avoiding allergens and using medicine do not control symptoms, or you have to take medicine all the time to control symptoms.
- Side effects of medicines are a problem.
- You want a treatment for the cause of your allergy, rather than treatment for just the symptoms.
- You have another condition that is being affected by allergic rhinitis, such as asthma.
- You want to lower the chance that you will develop asthma.
How Well It Works
Allergy shots are effective in treating allergic rhinitis and allergic asthma. The shots reduce symptoms in those allergic to pollens, animal dander, dust mites, mould, and cockroaches. Experts do not know how long allergy shots work after you stop getting the shots. Some people may not have their allergies return. Others may have allergies return within a few years.footnote 1
Although you still need to avoid allergens, you may be able to use less medicine or stop using medicines.
Allergy shots almost always are safe if given correctly. Redness and warmth at the shot site are common. Overall body reactions, such as hives, asthma symptoms, and low blood pressure, are not common. Because of the possibility of a life-threatening reaction (anaphylaxis), you get the shots where emergency care is available.
If you or your child has another condition, such as asthma, you may be more likely to have a severe reaction to the shots. You should have your asthma well controlled before you get allergy shots.
What To Think About
Although some of the costs may not be covered by your provincial health plan, allergy shots may cost no more than the combined cost of medicine, doctor and emergency room visits, and missed days of school or work over several years. But you may need to take regular shots for 3 to 5 years. And it may take a year or more for symptoms to improve. If the treatment schedule would be hard for you to follow, you may want to think about other options. During your treatment, you should see your doctor at least once every 6 to 12 months.
Allergy shots treat an allergy to just one allergen or a very closely related group of them, such as grass pollens. If you are allergic to more than one type of allergen, you may need to receive shots for each type of allergen to relieve all of your symptoms. The allergens can usually be combined into one or two shots.
Children younger than 2 should not have allergy shots. Children ages 3 to 4 may find it hard to get many shots over a long period of time. Talk with your doctor about whether allergy shots are right for your child.
Older adults may be taking medicines or have other medical conditions that may increase the risk of a severe reaction to allergy shots.
You must report any delayed reaction to an allergy shot. Late reactions can happen any time within 24 hours after a shot. Reactions may just affect the injection site (such as a large, red or raised area around the site) or they may affect your overall body (such as trouble breathing).
Pregnant women who are already taking allergy shots may continue them. But do not start taking them during pregnancy.
Allergy shots should not be used when you:
- Have had a recent heart attack, unstable angina, or other heart problems or are taking beta-blockers.
- Are unable to communicate (can't tell your doctor about reactions to shots). Most doctors do not give allergy shots to children younger than 5.
- Have an immune system disease (such as AIDS).
Sublingual immunotherapy may be another way to treat certain pollen allergies. Instead of getting shots, you dissolve a tablet under your tongue daily. Each tablet has a small amount of allergen in it. This treatment, like allergy shots, helps your body "get used to" the allergen, so your body reacts less to it over time. Oral and sublingual immunotherapy is being studied for other types of allergies also.
- Joint Task Force on Practice Parameters (2011). Allergen immunotherapy: A practice parameter third update. Journal of Allergy and Clinical Immunology, 127(1, Suppl): S1–S55.
Current as of: February 10, 2021
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Brian D. O'Brien MD - Internal Medicine
Adam Husney MD - Family Medicine
Martin J. Gabica MD - Family Medicine
Kathleen Romito MD - Family Medicine
Rohit K Katial MD - Allergy and Immunology
Current as of: February 10, 2021
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