More Info on Allergy Shots
Allergy shots are not started until after skin tests or blood tests have determined the exact culprits (see Allergy Diagnosis). Once the problem allergens are identified, the allergist prepares an allergy shot containing those allergens to begin the process of desensitization.
If the patient is very sensitive to a certain allergen, that allergen should be given in a separate allergy shot so local and systemic (whole body) responses can be carefully monitored. For example, some people are extremely allergic to grass pollen. If the grass pollens are in the allergy shot with other allergens, the desensitization to the other allergens might be delayed if reactions to the grass pollens mean maintaining or reducing the solution dose.
The amount of allergen in the first allergy shot is very dilute. The first allergy shot is usually 0.05 milliliters, resulting in a tiny amount of allergen actually being injected. This cautious approach decreases the chance of adverse reactions.
The allergy shots are given subcutaneously (under the skin) in the back of the upper arm. The regimen usually starts with allergy shots twice a week, gradually increasing the doses as long as no serious reactions occur.
A little bit of redness, itching, or swelling (less than 2 centimeters, or the size of a nickel) around the injection site is normal, and the dose may be increased at the next visit. Cold compresses, oral antihistamines, and topical corticosteroids can relieve these minor reactions.
If the site swells more than 2 cm or allergic symptoms develop, the allergist may decide to repeat the same allergy shot dose at the next visit or even reduce it, depending on the severity of the previous reaction.
The chances of having an adverse reaction to the injection are more common while the doses are being increased than once a maintenance dose is reached.
Anaphylaxis (a life-threatening reaction that causes blood pressure to plummet, the throat to swell, and airways in the lungs to constrict) is a slight but real risk with allergy shots. A shot of epinephrine, the same drug used to treat severe allergic reactions to bee stings, is used to treat anaphylaxis. Anaphylactic reactions may result in death, although this is rare.
The American Academy of Allergy and Immunology recommends that patients remain in the doctor's office for 20 minutes after receiving the allergy shot because reactions usually occur within that time. High-risk patients may have to wait additional time.
If no reactions occur, the amount of allergen in each allergy shot is increased until a maintenance dose is reached. For a very sensitive patient, the maximum dose may be the amount the patient can tolerate without a reaction. Others may be able to reach a predetermined amount that researchers have found to be necessary for optimal allergy relief.