Patient Information for Allergen Immunotherapy for Allergic Rhinitis
Allergen immunotherapy, commonly known as “allergy shots”, has been a mainstay of the treatment for allergic conditions for almost 100 years. In Canada, we are exposed to many of the allergens that have been proven to be effective in this type of treatment. Therefore, many allergists recommend this type of treatment for patients across the country. In this article, we will focus on the use of year round immunotherapy in allergic rhinitis and asthma. We will discuss potential benefits, patient and allergen selection, how the injections are given and safety issues.
Immunotherapy has been shown to be effective for most allergic conditions including allergic rhinitis, asthma, atopic dermatitis and insect sting allergy. As well, there are some studies suggesting that immunotherapy may actually prevent the onset of new allergies or even asthma. The concepts behind allergen immunotherapy are very different than the other common medical treatments that we use in treating allergic conditions such as allergic rhinitis and asthma. The mechanisms behind immunotherapy seems illogical to many. Patients are injected with gradually increasing doses of the allergens that were actually causing their original symptoms. There are several studies performed over the last few decades that have clearly shown that useful changes in the immune system occur with this approach to treatment. In fact, this is the only true treatment that changes the underlying immune problems that cause allergy.
Typically, we approach the treatment of allergic rhinitis by suggesting allergen avoidance measures for the identified allergens. These allergies are identified by skin testing by an allergist. Next, we would typically recommend using non-sedating antihistamines for mild patients and intranasal corticosteroid sprays for moderate and severe patients. Often, patients do not have an adequate improvement with these medical therapies or prefer not to take these medications on an ongoing basis. At this point, allergists may recommend allergen immunotherapy. We estimate that 70 to 80% of patients have a significant improvement with immunotherapy.
As noted previously, the important allergens for each patient are identified by the clinical history of symptoms and the allergy skin tests. In Canada, the most common allergens are dust mites, pets, pollens and molds. All of these allergens can be used in allergen immunotherapy. There are properly performed studies proving that these allergens are all useful for immunotherapy. Furthermore, we now have available standardized allergens for dust mites, cat, grass and ragweed available for patients in Canada. "Standardized" refers to the idea that these allergens are manufactured and tested so that their potency can be more accurately predicted. This has led to more effective immunotherapy that is easier to prescribe by allergists.
If the patient’s symptoms are not controlled by medical therapy, the allergist may prescribe the allergen immunotherapy. Generally, we try to include a maximum of three allergens per vial of serum. For example, we may mix dust mites with ragweed into one vial if a patient is allergic to both of them. Often, we must use two vials of allergy serum because a patient is allergic to several important allergens. Also, some allergens should not be mixed with some other allergens because some allergens can impact the potency of other allergens. Each vial is produced at a full strength concentration. Then that vial is further diluted into weaker vials that are 1/10 strength, 1/100 strength and 1/1000 strength compared to the full strength vial. The patient will receive gradually increasing volumes from the weakest strength vial up to the strongest strength vial. Ultimately, the patient will reach a maintenance volume from the strongest vial of allergen immunotherapy. The increasing doses are given once or twice per week by injection into the arm(s). When the maintenance dose is achieved, then the interval is gradually increased to once per month. Then the maintenance dose is given every month on a year-round basis. Usually, patients have clinical improvement in their symptoms within 6 to 12 months. Private and even provincial drug plans usually cover the cost of the immunotherapy extracts. The injections and medical care associated with them are paid for by public health coverage.
Unfortunately, there are some drawbacks to allergen immunotherapy. For example the length of time to increase the dosing of immunotherapy is usually about six months. Then, the patient stays on the monthly injections for approximately 5 years. One can see that there is a big time commitment to this treatment. Also, there is a risk of allergic reactions to the injections. Occasionally, these reactions can be life-threatening anaphylactic ones. Therefore, patients must wait 30 minutes after each injection in the physician's office. A physician must be present for all allergy injections. As well, generally patients with poorly controlled asthma or patients on beta-blocker medications should not receive allergy injections because of an increased risk of anaphylaxis.
In summary, allergen immunotherapy is a proven treatment in allergic conditions such as allergic rhinitis and asthma that can have a true disease modifying effect. Occasionally, we even are able to "cure" allergic rhinitis or asthma. It is a great option for patients who have not improved with standard medical therapies or who do not wish to stay on medical treatments indefinitely. Finally, a qualified allergist should prescribe immunotherapy and a physician must be present for each injection.
HIGHLIGHTS
- Allergen immunotherapy is the only treatment available that treats underlying allergies.
- There may be long-term benefits of receiving immunotherapy even after it is stopped.
- The injections must be given once or twice per week to increase dose then the interval is increased to every month. Generally, the immunotherapy is given for 5 years.
- There is a small risk of allergic reactions to the immunotherapy. Therefore you must wait 30 minutes after every shot.