Allergy injections are used to decrease your sensitivity to allergy-causing substances so that exposure to the offending allergens (pollens, dust, molds, etc.) will result in fewer symptoms. This does not mean that allergy shots are a substitute for avoidance of known allergens which is the treatment of choice.
Allergy injections have been shown to lead to the formation of blocking or protective antibodies and a gradual decrease in the allergy antibody level. These changes may permit you to tolerate exposure to the allergens with fewer symptoms. You, in effect, become protected from the allergens. The amount of this desensitization occurs to a different extent for each person.
Improvement should not be expected immediately. It usually develops gradually, and it may be a few weeks or months before you begin seeing improvement. About 90% of allergic individuals on immunotherapy experience significant improvement of their symptoms. The symptoms are reduced but may not go away completely.
Allergy injections are begun with a low dose. This dose is gradually increased on a regular (usually once or twice weekly) basis until a therapeutic dose (often called the “maintenance dose”) is reached. This frequency reduces the chances of a reaction and permits the maintenance dose to be reached in a reasonable amount of time. After the maintenance dose has been reached, injections are usually given every two weeks. The goal is to eventually spread the injections out to every three to four weeks over a period of several years.
The length of time required to experience symptomatic relief and reach maintenance varies according to the dosage at which we are able to initiate immunotherapy and individualized responses to the therapy. This time will be longer if there is swelling or other problems with the injections that require dosage adjustments. The time will also be prolonged if the injections are not received on a regular basis. For this reason it is important that the recommended schedule be followed. If it is anticipated that the injections cannot be taken regularly, allergy shots should not be started. Allergy injections may be discontinued if visits are frequently missed because there is an increased risk of reactions under those circumstances.
Local reactions (redness, warmth, swelling, itching, or tenderness at the site of the injections) may occur in most patients receiving injections. These local reactions usually subside in a day or so.
Large local reactions and generalized (systemic) reactions may occur in 1-5% of patients receiving allergy injections and usually occur during the build-up phase, although they can occur at any time during the course of treatment. These reactions necessitate a dosage adjustment. These generalized reactions may include, but are not limited to, any and/or all of the following symptoms: itchy eyes, nose, or throat, runny nose, nasal congestion, sneezing, tightness in the throat or chest, coughing, wheezing. Also, some may experience lightheadedness, faintness, a drop in blood pressure, nausea and vomiting, hives, and, under extreme conditions, shock. A severe systemic reaction potentially can be fatal, but this is very rare.
Allergy injections should be administered at a medical facility with a physician present since occasional reactions may require immediate therapy. Any medical facility that gives allergy injections should be equipped to treat any reaction that may occur. You should check with the facility to be certain that this is the case. As an added precaution, you must wait in the medical facility where you receive your injection at least 20 minutes after each injection so that in the unlikely event of a generalized reaction you can be quickly treated and kept under observation, thereby decreasing the likelihood of a more severe reaction.
Simple local reactions that consist of swelling of the arm, redness or tenderness at the site of the injection are best handled with simple measures such as local cold compresses or the use of medications such as antihistamines, aspirin, or Tylenol. You may experience an increase in allergy symptoms during the hours immediately following your injection. If this occurs, taking your antihistamine prior to getting the injection will help lessen these symptoms. You should always report any reactions to the nurse before receiving the next injection.