Oral immunotherapy (OIT) is a medical treatment that helps individuals with food allergies become less reactive to specific allergens. It involves giving increasing amounts of an allergen over time to raise the reaction threshold, reducing the risk and severity of accidental reactions.
The Science Behind Oral Immunotherapy
Oral immunotherapy works by gradually retraining the immune system to tolerate the food allergen. This involves controlled exposure to incrementally increasing doses. This consistent exposure helps to modify the body’s immune response, moving it away from an allergic state.
OIT induces several changes within the immune system. Initially, there might be a temporary increase in allergen-specific immunoglobulin E (IgE), responsible for allergic reactions, but this typically decreases as therapy progresses. Simultaneously, there is a gradual increase in allergen-specific immunoglobulin G4 (IgG4) antibodies. These IgG4 antibodies act as “blocking antibodies,” competing with IgE and neutralizing allergens before they can trigger a significant immune response.
OIT decreases T helper 2 (Th2) cell activity, which promotes allergic responses. There is also an expansion of regulatory T-cells (Tregs), which suppress allergic reactions and promote tolerance. These immunological shifts lead to desensitization, where the body can tolerate a larger amount of the allergen without reacting.
The OIT Journey: What to Expect
Oral immunotherapy involves distinct phases, beginning with initial dose escalation in a clinical setting. This phase, lasting several hours, involves patients receiving very small, gradually increasing amounts of the allergen under close medical supervision. Medical staff monitor for allergic symptoms to ensure patient safety and assess tolerance.
Following the initial escalation, patients enter a build-up phase with daily home dosing. Patients typically return to the clinic every one to two weeks for “updosing” appointments, where the allergen dose is incrementally increased. This phase continues for several months, with the goal of slowly increasing the amount of allergen the body can tolerate until a target maintenance dose is reached.
Once the maintenance dose is achieved, patients continue to ingest this amount of the allergen daily at home for an extended period, often for several years. Adherence to the daily dosing schedule is important to maintain the desensitized state. Patients are also advised to avoid vigorous exercise for a few hours after dosing and to communicate with their allergist if they are ill, as these factors can increase the risk of a reaction. While mild reactions like oral itching, rash, or abdominal discomfort can occur, more significant reactions are managed with guidance from the medical team, and patients are instructed to carry epinephrine.
Who Can Benefit from Oral Immunotherapy?
Oral immunotherapy is a treatment option for individuals with IgE-mediated food allergies, with common allergens treated including peanut, milk, and egg. Peanut OIT has an FDA-approved product for children aged 4 to 17 years. However, OIT can be considered for a range of ages, with some programs starting as young as 1 to 3 years old for milk, egg, and peanut allergies.
Patient suitability for OIT requires careful evaluation by an allergist. Factors such as the patient’s age, the specific allergen, and overall health status are considered. While OIT can benefit those with severe food allergies, it is not appropriate for everyone. For instance, individuals with uncontrolled asthma or certain conditions like eosinophilic esophagitis are generally not considered suitable candidates due to increased risks. An allergist will conduct allergy testing and review the patient’s medical history to determine if OIT is a viable and appropriate treatment path.