What is immunotherapy?
If you are allergic to one or more airborne allergens (like pollens or cat dander) and have nasal/eye symptoms, asthma, or both, you may be a candidate for immunotherapy, also known as shot therapy. If you read the descriptions of hay fever and asthma on this site, you have probably realized that there are very good, easy-to-use medications available for these conditions that help to control the symptoms, and can greatly improve quality of life. Whether the approach is a nose spray, an antihistamine pill, or an asthma inhaler, however, all of these treatment options are aimed at suppressing symptoms of the allergic condition, not at correcting the underlying allergy itself. While symptom suppression is, in itself, a desirable effect, this approach to treatment ignores the underlying source of the allergic disease – the body’s inappropriate immune response to a relatively innocuous airborne substance (for a more detailed description of this immune response, see the discussion of hay fever). Immunotherapy represents the only treatment option aimed at reversing the allergy itself, reducing symptoms by inducing a state of tolerance in which the body no longer reacts so vigorously to the allergens that previously were a source of misery.
What can I expect?
The process of immunotherapy is essentially very simple. Purified extracts from the allergens that cause your particular allergic condition are introduced to your immune system via an injection (usually in the upper arm) starting with miniscule amounts, and building gradually. The purpose of this slow building process is to induce you to tolerate exposure to increasing amounts of allergen without triggering an allergic reaction. In general, you can expect to return to the allergist’s office every 4 to 14 days for the next step up in your injection therapy (many patients adopt a weekly routine). Each injection is given into the subcutaneous fat layer just beneath the skin surface, is generally small in volume (half a cc or less) and does not cause significant pain, beyond the pinprick sensation of the needle itself. The gradual building process culminates in a predetermined maximum amount of allergen termed a “maintenance dose.” In a typical immunotherapy regimen, the build-up phase to reach maintenance requires six to twelve months of weekly visits. Once the maintenance dose is reached, you can plan to return on a monthly basis to receive the fixed maintenance dose. You and your allergist will determine the duration of your shot therapy maintenance, weighing the benefits to your allergic condition against the inconvenience of the monthly visits. Most scientific studies suggest that there is little added benefit of continuing the shots past 3-4 years of maintenance for airborne allergens.
What are the benefits and the risks of immunotherapy?
Approximately 4 out of 5 individuals experience an improvement in their allergic condition, ranging from reduction in symptom severity and required medication use to complete resolution of allergic symptoms. The risks associated with the shots are generally low, however, must be considered. Whenever we introduce into your body a substance to which you are allergic, we run the risk of triggering an allergic reaction. This risk is minimized by starting with extremely small doses and building gradually. The most common reaction is one that occurs locally at the injection site with mild itchiness, swelling and redness. This type of reaction typically lasts 1-2 hours and responds well to antihistamines. More rarely, reactions can spread beyond the injection site. These are referred to as systemic reactions, and they occur on average less than once in every 200 injections. Systemic reactions range from itchiness and/or hives in other areas of the body to a sense of chest tightness or wheeze, lightheadedness, or abdominal cramps. Systemic reactions, when they occur, are treated by the allergist in the office and typically resolve over 1-2 hours. When reactions do occur, the vast majority of them develop within 20-30 minutes of receiving the injection. For this reason most allergists require that every patient who receives immunotherapy plan to wait for about half an hour in the office after their injection.
Is immunotherapy right for me?
This is a decision that can only be determined through a dialog with your allergist. Many individuals with allergic asthma or rhinitis find sufficient relief with a simple medication regimen, and feel the time investment of immunotherapy is impractical. Some feel they would rather invest in trying to ameliorate the source of their allergies now by undertaking immunotherapy in order to reduce their medication requirements over the years to come. In children, in particular, there is good evidence that successful immunotherapy started early, as respiratory allergies begin to develop, not only reduces the allergic response to allergens to which the child is sensitive, but actually reduces the development of sensitivity to new allergens as the child grows. This protective effect suggests that shot therapy is not only inducing tolerance to the allergens one is receiving, but may actually be “retraining” the immune system away from its generally allergic predisposition.
Immunotherapy unfortunately in not effective for food allergies. However, it is extremely effective in providing protection against life-threatening reactions among those with allergy to stinging insects (wasps, hornets, bees, fire ants). In fact, unlike the case for asthma or allergic rhinitis where immunotherapy is one option to discuss, among sting-allergic individuals, shot therapy is strongly recommended. The process is very similar to that described above with similar risks, but the benefit is potentially life saving. If you believe you have an allergy to stinging insects, you would be wise to seek an allergist’s evaluation and seriously consider this approach.