Allergy shots, formally known as Allergen Immunotherapy (AIT), offer a long-term approach to managing persistent and severe allergic reactions. This multi-year commitment aims to fundamentally change the body’s response to environmental triggers like pollen, dust mites, or pet dander. Understanding the timeline for AIT is important for anticipating when to expect significant relief from symptoms. This article provides an overview of the immunotherapy process, its mechanisms, and the expected schedule for achieving lasting results.
Defining Allergen Immunotherapy
Allergen immunotherapy (AIT) is a specific treatment designed to desensitize the immune system to identified allergy triggers. Unlike medications that only mask symptoms, AIT addresses the underlying biological cause of the allergic reaction. The treatment involves administering small, controlled doses of the specific allergen extract through subcutaneous injections, or “shots.”
The fundamental mechanism of AIT is shifting the immune response away from a hyperactive allergic state. Allergies are driven by T helper 2 (Th2) cells, which lead to the production of Immunoglobulin E (IgE) antibodies. Repeated exposure from the shots encourages the body to produce regulatory T cells, which help suppress the Th2 response.
This shift also leads to the production of allergen-specific blocking antibodies, primarily Immunoglobulin G4 (IgG4). These IgG4 antibodies interfere with the allergic cascade, preventing the allergen from binding to IgE on mast cells and basophils. By retraining the immune system to tolerate the allergen, AIT works to reduce both the severity and frequency of allergic episodes.
The Build-Up and Maintenance Phases
Allergen immunotherapy is structured into two distinct phases: the build-up phase and the maintenance phase. The initial build-up phase gradually increases the amount of allergen administered to reach the maximum effective dose. This phase typically lasts between three and six months, varying based on individual response and the treatment schedule.
During the build-up phase, injections are administered frequently, usually one to three times per week. This frequent schedule ensures the immune system is consistently exposed to increasing allergen concentrations without causing severe reactions. Reaching this maximum tolerated dose, also known as the maintenance dose, signals the transition to the next stage.
The maintenance phase is a considerably longer commitment, typically lasting three to five years. Once the maintenance dose is achieved, the frequency of injections is significantly reduced, usually to once every two to four weeks. This extended period is crucial for solidifying immune changes and establishing long-term tolerance to the allergens.
When Patients Notice Symptom Relief
Symptom improvement is a gradual process and not an immediate effect of beginning allergy shots. Patients should not expect significant relief during the early weeks or months of the build-up phase, as initial injections are low-dose and focus on safely introducing the allergen.
Many patients begin to notice minor improvements in symptoms around six to twelve months after starting treatment. This typically corresponds to the time they are nearing the end of the build-up phase or transitioning into maintenance.
Significant, lasting relief is typically observed during the second year of treatment, once the patient is well into the maintenance phase. This delayed timeline reflects the time required for the body to shift from an allergic response to a tolerant one. Consistent adherence to the injection schedule is paramount, as missing doses can delay progress and require a temporary return to more frequent injections.
Duration of Immunity After Treatment
The benefits of allergen immunotherapy are designed to be long-lasting, extending well beyond the treatment course. After successfully completing the full recommended three-to-five-year course of maintenance therapy, the immune system is fundamentally reprogrammed. This leads to sustained immune tolerance, meaning the body reacts minimally or not at all to the allergens.
Clinical studies indicate that symptom relief often persists for many years after the shots are stopped. For a large percentage of individuals who complete the full course, the long-term benefits may be permanent. If a small number of patients experience a gradual return of symptoms, a physician may recommend a short course of booster shots to re-establish immune tolerance.