Oral immunotherapy (OI) is a form of desensitization designed to treat food allergies. It consists of daily ingestion of the food allergen in question (precisely measured) following a schedule starting with minimal doses (below the threshold reactive dose of each patient) and progressing to doses equalling normal food portions. Once these maintenance doses are achieved, the patient can continue to ingest the food on a regular basis in order to maintain protection.
The three potential benefits of oral immunotherapy are the following:
- Protecting against reactions in case of accidental exposure to the food in question
- The ability to reintegrate the food into the normal diet
- Definitive resolution of the allergy (sustained tolerance)
The rates of success for the first two objectives are approximately 80% in studies, and can exceed 90% in private clinics, possibly because of an increased flexibility of existing protocols. The achievement of these objectives is associated with a major improvement in the reduced quality of life associated with food allergy, notable with regard to the emotional impact, hypervigilance, social limitations, and anxiety related to eating.
Sustained tolerance (the 3rd objective), which is defined as the persistence of tolerance to the food after a prolonged interruption of daily maintenance doses may follow after 4-5 years of treatment in about half of patients treated for eggs and peanuts. This rate can be substantially higher in younger children (12 to 48 months) who are allergic to peanuts.
OI must be performed under strict medical supervision because it is associated with certain risks of reaction when taking the doses. According to studies, between 50 and 95% of patients report allergic symptoms when taking doses of the food, although predominantly minor (oral itching, gastric upset) and easily controlled with antihistamines in 95% of cases. Between 2 and 5% of patients will need to administer an epinephrine auto-injector while undergoing treatment, generally because of asthma symptoms. Finally, 2.7% of patients can develop an inflammation of the esophagus with this treatment (eosinophilic esophagitis). However, this inflammation is transitory and has disappeared when stopping the doses in all cases reported to date.
In a recent survey in the United States, 13% of allergists reported practicing OI and 40% could identify a colleague offering this service in their region. The exact percentage of allergists practicing oral immunotherapy in Québec and elsewhere in Canada is unknown, but the availability is for the moment limited because of curtailed access to hospital services and the human resources required to offer this treatment in a secure and supervised manner. Nevertheless, it is quite likely that because of its efficacy in inducing desensitization, OI will find a place in the therapeutic options of Québec allergists in the very near future.
For references and a more detailed description of the literature of OI, please refer to a resumé for health care professionals at OIT 2016.pdf (French version).
Additional information may be found in our research articles.
Philippe Bégin MD, PhD, FRCPC
(translation: Andrew Moore, MD, FRCPC)