This article is the first in an ongoing series we are going to feature on food allergy therapies. Our goal in this series is to provide an overview of the various forms of food allergy therapies currently being offered in North America, with a focus on Canada.
At the outset, it’s important to keep in mind that there is currently no cure for food allergy, and the treatments we will be looking at aren’t equally effective for all patients. It is also important to note that although there are allergists who offer OIT in the United States and Canada, this is not yet a standard treatment offered by allergists, and OIT is mainly conducted as part of clinical research trials. Nevertheless, these treatments hold promise for many, and have been life-changing for some.
This month, our focus is on Oral Immunotherapy (OIT). We had the pleasure of interviewing Tosha Freitag, RN, MN, research nurse, who works with Dr. Susan Waserman, Allergist & Clinical Immunologist at McMaster University.
Can you tell us a bit about OIT and what it involves? What is the goal of OIT?
OIT refers to a protocol in which a patient consumes small amounts of an allergenic food, such as peanut, in a controlled environment (allergy clinic/hospital). The food is introduced slowly to the immune system in the hope of the allergic individual tolerating the food without overreacting to it. The particular food is ingested daily and is gradually increased to a determined maximum amount (maintenance dose) with the goal of allowing the food to eventually be consumed without an allergic reaction (i.e., desensitized). Desensitized means that the person can ingest much more of the food than they could before OIT of the allergenic food, which will protect them in the event of an accidental exposure.
Who is qualified for OIT? Are there any disqualifying factors?
An allergist needs to assess their patients to determine their qualification for OIT. Any healthy child without significant health conditions can qualify for OIT. The child should be old enough to follow instructions and verbally report symptoms/side effects. Children with chronic, uncontrolled asthma should not undergo OIT, as this could put them at higher risk for a severe reaction.
How eﬀective is OIT at desensitizing for food allergens?
Desensitization can be achieved in approximately 50-80% of children for any food. The rate of permanent tolerance is unknown (i.e., being able to tolerate the allergen without taking a daily maintenance dose), but appears to be low for foods such as peanut; the longer the duration of OIT, the better the outcomes. Long-term studies are still needed.
What kind of maintenance dose of the allergen is required, and do patients need to take it every day for the rest of their lives to maintain tolerance?
The maintenance dose of the allergen is pre-determined prior to starting the desensitization process, and the amount depends on the specific allergen. The maintenance dose of the allergen is often similar to that reported in studies. For example, peanut desensitization reaches a maximum of between 300-500mg of peanut. The maximum amount achieved is the daily amount that must be consumed for maintenance. In our study, the kids work up to 500mg of peanut, which is equal to two peanuts. Therefore, their maintenance dose is two peanuts every day.
For milk desensitization, the literature indicates that the child needs to work up to one cup of milk. After one cup of milk is safely achieved without a reaction, the child will need to consume a cup of milk daily as a maintenance dose. This can be split into two doses: A half-cup at breakfast, and another half-cup at dinner.
Due to the lack of long-term studies on OIT, currently, the allergen must be ingested daily to maintain tolerance. [As Dr. Waserman points out, once the individual stops eating it daily, sensitivity often returns.]
How long does the OIT process usually take, from beginning to end?
Duration depends on the starting and ending dose. If the starting dose is 1mg and the ending dose is 500mg, based on the protocol we used, it will take about six months uninterrupted.
What costs are involved in OIT, and are any covered by provincial health plans?
The costs of OIT include staff – for example, a nurse – as well as the expense of a pharmacist, who measures peanut powder and places them in packages or capsules. These measurements are precise and time consuming, as ideally, each child has 14-21 packages of one dose given to them every two weeks (with an extra week given in case of illness) over the duration of the study. Costs also include the peanut powder, and any extra supplies needed to prepare the doses. In the case of a research study, the study bears the cost.
OIT is is not covered by provincial health plans as it is not routine or a mainstream practice in Canada, but still largely within the realm of research. Therefore, patients have to cover the expense out of pocket if they choose to undergo OIT by a practitioner who is performing it.
Is there anything else you would like our readers to know about OIT?
OIT must be conducted in a controlled environment by trained medical staff members. OIT does involve some risks, and not all children respond the same or are successful. Often side effects are experienced in the initial dose escalation phase at home (oral pruritus/itchiness, abdominal discomfort, and rashes) which do subside after a few days on the new escalated dose. It is often helpful to have a medical staff member available for the families by phone or email to provide ongoing information and reassurance during the escalating dose phase.
An emergency plan needs to be communicated with the family since severe reactions requiring epinephrine have been reported on dose escalation. Lastly, there are factors that increase a child’s risk of reaction, even to previously tolerated doses, such as exercise, infections, ingestion of the allergen on an empty stomach, menstruation, asthma exacerbation and seasonal allergies.
Read the OIT experiences of two families. Their stories highlight how individuals respond differently to medical treatments.