Allergy shots are a form of treatment called immunotherapy. Each allergy shot contains a tiny amount of the specific substance or substances that trigger your allergic reactions. These are called allergens. Allergy shots contain just enough allergens to stimulate your immune system — but not enough to cause a full-blown allergic reaction.
Over time, your doctor increases the dose of allergens in each of your allergy shots. This helps get your body used to the allergens (desensitization). Your immune system builds up a tolerance to the allergens, and your allergy symptoms diminish over time.
Why it's done
Allergy shots may be a good treatment choice for you if:
Allergy shots can be used to control symptoms triggered by:
Allergy shots aren't available for food allergies or chronic hives (urticaria).
Most people don't have much trouble with allergy shots. But they contain the substances that cause your allergies — so reactions are possible, and can include:
If you get weekly or monthly shots on a regular schedule without missing doses, you're less likely to have a serious reaction.
Taking an antihistamine medication before getting your allergy shot can reduce the risk of a severe reaction. Check with your doctor to see if this is recommended for you.
The possibility of a severe reaction is scary — but you won't be on your own. You'll be observed in the doctor's office for 30 minutes after each shot, when the most serious reactions usually occur. If you have a severe reaction after you leave, return to your doctor's office or go to the nearest emergency room.
How you prepare
Before starting a course of allergy shots, your doctor may use a skin test to determine that your reactions are caused by an allergy — and which specific allergens cause your signs and symptoms. During a skin test, a small amount of the suspected allergen is scratched into your skin and the area is then observed for about 15 minutes. Swelling and redness indicate an allergy to the substance. Your doctor may also use an allergy blood test.
When you go in for allergy shots, let the nurses or doctors know if you are feeling unwell in any way. This is especially important if you have asthma. Also let them know if you had any symptoms after a previous allergy shot.
What you can expect
Allergy shots are usually injected in the upper arm.
To be effective, allergy shots are given on a schedule that involves two phases:
In some cases the buildup phase is accelerated, which requires several injections of increasing doses during each doctor visit. This can decrease the amount of time you need to reach the maintenance phase and get relief from allergy symptoms, but it also increases your risk of having a severe reaction.
Allergy symptoms won't stop overnight. They usually improve during the first year of treatment, but the most noticeable improvement often happens during the second year. By the third year, most people are desensitized to the allergens contained in the shots — and no longer have significant allergic reactions to those substances.
After a few years of successful treatment, some people don't have these significant allergy problems even after allergy shots are stopped. Other people need ongoing shots to keep symptoms under control.
Last Updated: 2012-02-22
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