There are three basic methods for the treatment of all allergic diseases, including bronchial asthma. These are:
- Environmental control (or allergen avoidance)
- Drug therapy
Most physicians will emphasize allergen avoidance and the use of inhaled medications as the first line treatment for asthma. In some cases, these treatments are only partially effective, and allergen immunotherapy becomes necessary. Allergen immunotherapy should also be considered if the amount of medication a patient must take is so excessive that it becomes a burden or if there are significant side effects.
Allergen immunotherapy involves the injection of the “allergen” to which the patient is sensitive. The injections are designed to alter the patient’s immune system so that they no longer react to the allergen. The mechanism by which immunotherapy works is not known. However, it has been demonstrated to be effective for both allergic rhinitis and asthma. Immunotherapy for pollens, cats, house dust mites and molds have all been studied, and injection of each of these allergens has been shown to completely or partially decrease the patient’s sensitivity and thus decrease their symptoms. For the asthmatic patient, immunotherapy decreases inflammation in the lungs resulting in less symptoms and reduced need for asthma medications.
In practice, when immuntherapy is started, injections are given once or twice a week. Over a period of months, the dose of allergen is increased until a maintenance level of allergen is achieved. The frequency of injections is then decreased to once a month. The change in the immune system seen with immunotherapy takes place over a prolonged period of time. Thus, it may take several months of injections before any improvement is noticed, and the full benefit may not be realized for 6 months or more. If no improvement is seen after two allergy seasons using adequate immunotherapy doses, then the treatment should be stopped. If there is improvement, then the injections should be continued for 3 to 5 years. The injections are then discontinued and many patients will have prolonged benefit even though they are not receiving injections.
Most patients will have little or no side effects from immunotherapy. However, life-threatening reactions to immunotherapy do occur. Thus, allergy immunotherapy should only be administered in a physician’s office where trained personnel and cardiopulmonary resuscitation equipment are available. Immunotherapy should not be started during pregnancy. However, it may be continued during pregnancy as long as there are no symptomatic reactions.