What is immunotherapy?
Immunotherapy or “allergy shots” is a very effective treatment used to relieve allergy symptoms from hay fever and allergic asthma by administering injections of substances such as pollens, mold spores, dust mites, animal dander or insects to which an individual has been found to be allergic by skin testing. The mechanisms of its effects are the subject of ongoing research. However, immunotherapy initiates processes that seem to “turn off” the abnormal immune reaction that we term “allergy”. This will allow better control of environmental allergies and asthma and reduce the dependency on medication.
When an allergic person is exposed to an allergic substance (such as cat dander), he or she may develop symptoms of sneezing, runny nose, nasal congestion, watery eyes, chest tightness or wheezing. Various cells that line the nose and the airway actually release chemicals termed mediators that cause allergic symptoms.
Allergen immunotherapy has traditionally been administered by subcutaneous injections. Newer forms of treatment such as sublingual immunotherapy have been developed that are more convenient and may be suitable for selected patients.
How are injections given and for how long?
During the “build up” phase, increasing doses of allergy injections are given once or twice a week until a predetermined target or maintenance dose is achieved. This usually takes 3-4 months (16-24 injections). Once the maintenance dose is achieved, shots are usually administered every 2 to 3 weeks over the ensuing several years of treatment. Clinical improvement with immunotherapy usually occurs within the first year. In a small percentage of patients, there is no improvement and in this case, immunotherapy is discontinued. However, if symptoms do improve, injections are usually continued for at least 4-5 years of maintenance therapy. At that time, you and your doctor will make a joint decision about whether to gradually taper and discontinue injections or to continue treatment.
Reactions to immunotherapy
Local reactions (swelling, itching or tenderness at the site of the injection) may occur in most patients receiving injections. These local reactions usually subside in a day or less.
Large local reactions and generalized (systemic) reactions may occur in 1-5% of patients receiving allergy injections and usually occur during the buildup phase although they can occur at any time during the course of treatment. These reactions necessitate a dosage adjustment. The generalized reactions may consist of any or all of the following symptoms: itchy eyes, nose or throat, runny nose and nasal congestion, sneezing, tightness in the throat or chest, coughing, wheezing. Also, some may experience lightheadedness, faintness, nausea and vomiting, hives and , under extreme conditions, shock. Reactions can be serious but rarely fatal.
Allergy injections should be administered at a medical facility with a physician present since occasional reactions may require immediate treatment. 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 observed, thereby decreasing the risk of a more severe reactions.