Allergen immunotherapy, also known as allergy shots, can help people who suffer from allergic rhinitis (nasal allergy), allergic conjunctivitis, and allergic asthma caused by allergens such as pollen, mold, animal dander, and house dust mites.
Patients who receive immunotherapy are safely injected with small but increasing amounts of specific identified allergens over a period of time. This process suppresses allergic reactions and can induce improvement that continues after the injections are stopped. Immunotherapy also has been proven to markedly reduce the development of new allergies and, in children, can prevent the progression from allergic rhinitis to asthma. Immunotherapy is also recommended for treatment of allergic asthma.
Over the last century much has changed in the standardization of extracts and in the number of evidence-based studies proving effectiveness. Immunotherapy works like a vaccine. The body responds to the injected amounts of a particular antigen given in gradually increasing doses by developing immunity or tolerance to the allergens. As a result allergy symptoms decrease when the patient is exposed to that allergen in the future.
There are two phases to immunotherapy. The buildup phase involves injections with increasing amounts of the allergens until the effective dose is reached. The maintenance phase begins once the effective therapeutic dose is reached. Maintenance doses have been found to be effective in clinical trials.
The benefits of immunotherapy are dose related. In the past, low levels of antigen were given and had little or no beneficial effect. Also, if not all of the important allergens are identified correctly, the allergy vaccine may not be effective. Board-certified, fellowship-trained Allergy and Immunology specialists are trained to provide accurate diagnosis and effective therapy.
Traditional Immunotherapy, involves giving subcutaneous (just under the skin) injections once or twice a week with increasing amounts of allergens. Maintenance doses usually are achieved after 37 injections. In one recent study this was accomplished in an average of 23 weeks. Only ~60% of patients starting traditional immunotherapy reached maintenance. The long delay before clinical improvement and difficulty making so many office visits were the most common reasons for abandoning immunotherapy. Mild systemic reactions occur in ~3% of patients. Fatal allergic reactions have occurred. There have been no fatal reactions in the US for several years, at least in part because of multiple procedures that have been introduced to minimize risks of reactions.
Cluster Immunotherapy is a new approach that allows much faster increases in doses, fewer office visits, fewer injections, faster clinical improvement, and therefore a much higher proportion of patients reaching maintenance. In a typical cluster protocol 4 or 5 increasing doses are given over 60 to 80 minutes. The patients are then monitored for one hour to detect and treat any local or systemic reaction that might occur. This is done two times a week for 2 weeks. At that point clinical improvement usually is apparent. Doses are then given once or twice a week until the maintenance dose is achieved. Then the doses are spread out until the maintenance dose is given once a month.
One recent study compared 76 cluster immunotherapy patients to 91 traditional immunotherapy patients in a single practice. Cluster immunotherapy required fewer office visits, fewer injections, fewer days to maintenance doses, and a higher proportion of patients reaching maintenance as shown in the table. Systemic allergic reactions were more common among cluster patients, but no serious reactions occurred in either group.
Cluster immunotherapy offers clear potential advantages for many patients. If allergen avoidance and medications are working well, and the doctor’s office is convenient, traditional immunotherapy might be the most appealing approach. For those people who need or want more rapid clinical improvement and fewer office visits, cluster immunotherapy is an acceptably safe and effective new allergy treatment.
-Andrew Smith, MD and Timothy J. Sullivan, MD