An allergy shot is medicine that is injected into your body. The medicine contains a small amount of an allergen. This is a substance that causes an allergic reaction. Examples of allergens include:
A doctor or nurse gives you shots over the course of 3 to 5 years. This series of allergy shots may help reduce your allergy symptoms.
First, work with your doctor to identify which allergens are causing your symptoms. This is often done through allergy skin testing or blood tests. Only the allergens you are allergic to are in your allergy shots.
Allergy shots are only one part of an allergy treatment plan. You may also take allergy medicines while having allergy shots. Your doctor may recommend that you reduce your exposure to allergens, as well.
How do allergy shots work?
Allergy symptoms occur when your immune system tries to attack an allergen in your body. When this happens, your body creates mucus. This can cause bothersome symptoms in the nose, eyes, and lungs.
Treatment with allergy shots is also called immunotherapy. When a small amount of an allergen is injected into the body, the immune system makes a substance called an antibody that blocks the allergen from causing symptoms.
After several months of shots, some or all of your symptoms may be relieved. Relief can last several years. For some persons, allergy shots can prevent new allergies and reduce asthma symptoms.
Who can benefit from allergy shots?
You may benefit from allergy shots if you have:
Asthma that is worsened by allergies
Allergic rhinitis, allergic conjunctivitis
Insect bite sensitivity
Eczema, a skin condition that can be caused by dust mite allergy
Allergy shots are effective for common allergens such as:
Weed and tree pollen
Mold or fungi
Adults (including the elderly) as well as children can receive allergy shots.
Your doctor is not likely to recommend allergy shots for you if you:
Have severe asthma.
Have a heart condition.
Take certain medicines, such as ACE inhibitors or beta blockers.
Are pregnant. Pregnant women should not begin allergy shots. But they may be able to continue allergy shot treatment that was started before they became pregnant.
Food allergies are not treated with allergy shots.
Getting your allergy shots
Allergy shots are given in your doctor's office, usually in the upper arm. The typical schedule is:
For the first 3 to 6 months, you receive shots about 1 to 3 times a week.
For the next 3 to 5 years, you receive the shots less often, about every 4 to 6 weeks.
Keep in mind that many visits are needed to feel the full effects of this treatment. Your doctor will assess your symptoms on occasion to help decide when you can stop receiving the shots.
An allergy shot may cause a reaction on the skin, such as redness, swelling, and itching. Some people have mild nasal stuffiness or runny nose.
Though rare, an allergy shot can also cause a severe life-threatening allergic reaction called anaphylaxis. As a result, you may need to do the following:
Stay in your doctor's office for 30 minutes after your shot to check for a reaction.
Take an antihistamine or another medicine before your allergy shot appointments.
Reactions to allergy shots can be treated in your doctor's office right away.
When to call the doctor
Call the doctor if:
You continue to have symptoms after several months of allergy shots
You have questions or concerns about the allergy shots or your symptoms
You have trouble keeping appointments for your allergy shots
Cox L, Nelson H, Lockey R, et al. Allergen immunotherapy: a practice parameter third update. J Allergy Clin Immunol. 2011;127(1 Suppl):S1-S55.
Golden DBK. Insect allergy. In: Adkinson NF Jr., Bochner BS, Burks AW, et al., eds. In: Middleton’s Allergy Principles and Practice. 8th ed. Philadelphia, PA: Elsevier Mosby; 2013:chap 78.
Sur DK, Scandale S. Treatment of allergic rhinitis. Am Fam Physician. 2010;81:1440-1446.
Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.