Oral immunotherapy

Oral immunotherapy is a form of treatment for food allergies. It consists of the introduction into the daily diet of a small quantity of food to which one is allergic, below the quantity required to cause a reaction, with a goal of inducing tolerance to a certain amount of the food in question. Over time, regular exposure to the food will reduce the antibodies that arm the allergy cells, thereby increasing the tolerance threshold of the food. The daily dose of the food can be increased periodically in the Allergist's office until the target dose is obtained. This can offer a level of desired protection against accidental exposure, and one may be able to integrate the food into the diet accordingly, depending on the case and the objectives of the parents.

Desensitization

The state of desensization as described above is temporary. If daily ingestion of the food is stopped, the antibodies will progressively rearm the allergy cells and the protection will be lost in a more or less rapid fashion, depending on the patient. It is therefore important that the patient is motivated to eat the food on a daily basis to maintain the protection over the short-term. In case of a reaction to this dose, there is a tendancy to reduce the daily dose, rather than stop completely, to prevent the loss of this state of desensitization.

The sustained effect

Over the long term, the regular exposure to the food allows the body to produce protective antibodies which interfere with those causing the allergy. These protective antibodies perist after stopping the daily dose and are generally sufficient to protect the patient from severe reactions from small quanitites of the food. Thus, after 3-5 years of treatment, if the patient chooses to stop taking daily doses of the food, they will maintain a certain level of protection, which allows them to be exposed to small quanitities of the food without the risk of anaphylaxis. Depending on the food and personal preferences, this protection can suffice according to the patient's objectives (eg, protection against accidental nut exposure). In other situations, patients will prefer to continue immunotherapy over the long term to be able to expose themselves to larger quantities of the allergen.

Complete remission

When started at a young age, soon after the diagnosis of an allergy, immunotherapy can also lead to complete remission of the allergy. The more time that passes, and the greater the production of antibodies, the more difficult it is to definitively treat the condition. There is therefore a window of opportunity in the first years of life to intervene with a curative approach. Given the issues of access, programs are being developed to allow families to initiate the desensitization process before seeing the allergist, so as not to miss the window of opportunity to induce allergy remission.

Side effects

Experience with oral immunotherapy varies from one patient to another, depending on the severity of their allergy, the fixed objectives, and biological factors that are not completely elucidated. The majority of patient will have minor symptoms, especially of the mouth and the stomach, at a certain point in the therapy. These are generally easy to treat, either by slowing the speed of progression of the daily dose, or by adding medications to take with each dose.

Certain patients may present with more important reactions, requiring the use of an epinephrine auto-injector. Overall, studies show that there is a greater chance of using the auto-injector while undergoing oral immunotherapy than with continued strict avoidance of the allergen. In retrospect one can generally explain reactions at normally tolerated doses by the presence of "co-factors" of anaphylaxis, elements which render us more likely to have reactions. The classical co-factors include undertaking physical exercise, fever and infections, heat waves, the intake of alcohol, using anti-inflammatories (NSAIDS) such as ibuprofen or aspirin, or during the period of menstruation. It is therefore important to follow the Allergist's instructions in order to avoid these co-factors immediately before taking a dose, and to be ready to use the epinephrine auto-injector as needed in case of a reaction.

Rarely, certain patients will develop an allergic irritation of the esophagus or the stomach which may require discontinuation of therapy.

Conversely, in infants who are treated shortly after diagnosis before the allergy antibodies have had time to amplify, reactions are much less frequent and generally not very significant.

Target dose

The choice of the targeted maintenance dose varies depending on the patient's goals. While patients with allergies to milk or eggs will generally want to reach higher doses to incorporate food into the diet, a patient with an allergy to nuts or peanuts may be satisfied with a small dose that simply provides protection against accidental contact.

It is important to note that studies have shown that doses as small as 4 mg (1/50 peanut) are sufficient to induce remission in infants and to generate protective antibodies in older patients. Small-dose immunotherapy is therefore an interesting avenue for severely allergic patients, those who do not like the taste of the food, or those who have had a failure with the larger doses.

References

1. Kim EH, Keet CA, Virkud YV, Chin S, Ye P, Penumarti A, et al. Open-label study of the efficacy, safety, and durability of peanut sublingual immunotherapy in peanut-allergic children. J Allergy Clin Immunol 2023;151(6):1558–1565.

Additional information may be found under our research articles.

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Anna Voia et Philippe Bégin MD, PhD, FRCPC

(translation: Andrew Moore, MD FRCPC)

Updated 11/2024