What is Oral Immunotherapy (OIT)?
Oral Immunotherapy (OIT) — a process that regularly exposes the patient to increasing amounts of the foods they are allergic to, with the goal of desensitising the body and protecting against anaphylaxis from accidental exposures.
How does OIT work?
Initially, we need to confirm that the patient is definitely allergic to peanut. This is a very important step that requires thorough consultation, appropriate skin and/or blood testing, and possibly an oral food challenge (OFC). We would then discuss starting OIT in our clinic with a very small dose of the food, which you would then continue to take at home. Every 2 weeks or so, you would return to clinic for a dose increase, and once we achieve the target dose (300mg of peanut protein), you would continue to take that daily for at least 1 or 2 years. By gradually increasing the amount of peanut you are exposed to, and by maintaining very regular intake, your immune system becomes more “used to” the allergen, and less likely to react. This increase in threshold (the amount required to trigger allergic symptoms) and decrease in reactivity (less severe symptoms when reacting) is called desensitization.
Is an Oral Food Challenge (OFC) necessary to undergo OIT?
In the strictest sense, no; it is possible (and in some places common) to offer OIT without an OFC. That said, this leaves the distinct possibility that the person is not truly allergic to the food in question, and that the (expensive and time-consuming) OIT may have been unnecessary. In patients with recent convincing reactions and convincing supportive test results, an OFC may be unnecessary, but in our experience, a baseline food challenge can be incredibly helpful. In some cases, the OFC is successful, confirming that the allergy has in fact resolved, and OIT is then unnecessary. In other cases, the OFC helps the patient understand their allergy better, the symptoms to watch for and the appropriate treatment for such reactions. Additionally, the OFC can establish the allergic person’s current threshold, which can help guide OIT dosing, potentially saving a lot of time, weeks or even months of updosing.
Is OIT a cure – will I be able to eat peanut normally after?
This is a complicated question. For some patients, especially very young children, OIT may in fact be a “cure”, inducing full tolerance and allowing them to eat peanut normally afterwards. For most patients, however, OIT is not a cure, but rather a desensitization – a temporary and reversible state of being less sensitive. In order to maintain desensitization, you will continue to eat the amount of peanut you have been desensitized to on a regular basis.
What is the difference between tolerance and desensitization?
True tolerance means being able eat the particular food as much or as little as you wish without risking an allergic reaction. This is the case for the overwhelming majority of foods we eat on a daily basis. Desensitization means that you are able to tolerate more of the food without reacting, sometimes a lot more, but you have to keep eating the food regularly to maintain that desensitized state. If you are desensitized, and stop eating the food, the allergic symptoms would return quickly unless true tolerance has developed.
Am I a good candidate for OIT?
This is a very individualized issue, and requires shared decision making, where the risks, benefits and alternatives are considered as well as the impact of doing nothing. In theory, anyone with a confirmed IgE-mediated peanut allergy is a candidate for OIT, however it is never that simple. Younger children are better candidates than older children, who in turn are better candidates than adults, where the success rates are fairly low. You will have a full assessment by Professor Fox, who will help determine if OIT could be helpful for you. Families should also be prepared for a daily commitment to dosing at home and regular visits for many months if they wish to go down the OIT route.
My child has asthma, can I still undergo OIT for my peanut allergy?
Yes, but the asthma must be very well-controlled, and it will be critical that you follow the Asthma Action Plan you and your doctor have developed very closely. Poorly controlled or unstable asthma is a major risk factor for more severe allergic food reactions, and it is essential that your airway inflammation and hyper-responsiveness (twitchiness) be minimized throughout. Of course, this should actually be the case for your child’s asthma even if you don’t undergo OIT!
Can I have an allergic reaction going through OIT?
It is actually common and expected to have allergic reactions while going through OIT. Mild reactions, such as an itchy mouth or throat, or mild stomach-ache, occur in a majority of OIT recipients, and can be taken as a good sign that your immune system is busy working with the allergen as expected. Severe reactions are much less common; however there is always a risk of anaphylaxis, and it is important to understand this and be prepared for this possibility. There are several strategies to try to minimize the risk of severe reactions, and we will spend time counselling you on these.
What are some of the factors that increase the risk of a severe reaction to OIT?
As mentioned above, uncontrolled or unstable asthma is a major risk factor. Viral infections, especially with a fever, can also increase the risk. We will explain how to adjust your dosing if you are unwell. It is important to avoid vigorous activity for a couple of hours after dosing, as this can also increase the risk. We have also learned that fatigue can play a role, so it is important to get ample rest, and to be aware that dose adjustments may be necessary in some circumstances. Very importantly, missing OIT doses increases the risk for reaction, and it is critical to be consistent in the dosing schedule.
Do I need to take any specific medications in addition to OIT?
Of course, it is important to maintain good control of any asthma or other allergic conditions throughout the OIT process, as well as any other medical conditions you may have. We may also advise you to take a non-sedating antihistamine daily throughout the build-up phase, to help minimize mild allergic symptoms, and to improve the immunogenicity (effectiveness) of the OIT. This is usually stopped once the target maintenance dose is achieved.
Can you treat multiple food allergens simultaneously with OIT?
Yes, we can treat multiple foods (eg peanut, wheat, sesame, treenuts, milk and egg) that you are allergic to at the same time. It is possible to build these up simultaneously, although many patients prefer to reach maintenance dosing with one food before starting another.
I had a bad allergic reaction in the past, is it safe for me to do OIT?
Yes, you may be able undergo OIT even if you have had severe allergic reactions in the past but this will be subject to detailed discussions with Prof Fox. In fact, studies suggest that patients with lower thresholds or more severe symptoms at baseline may benefit the most from OIT.
What is Xolair, how does this impact OIT?
Xolair (omalizumab) is an injectable anti-IgE biological therapy that works by inhibiting the allergic reaction process. Studies suggest that pre-treatment with a short course of Xolair allows for a faster and safer OIT buildup, reaching the target maintenance dose in a fraction of the time. As a biological therapy, Xolair is fairly expensive, and as it is not formally approved for use with OIT, it will not be covered by your insurance provider. This is something we would again discuss and consider on a case-by-case basis.
I may have trouble coming into the clinic every 2 weeks for OIT dose increases, will this be a problem?
Certainly all dose escalations should be done in clinic for safety reasons, however it is absolutely possible (and in fact common) to individualize the OIT schedule to optimize convenience. Although it may take longer to achieve maintenance dosing in these cases, that in itself is not a problem.
How long does the OIT process continue for?
This is a tricky question, and again highly individualized. In general, the build-up period takes several months, and sometimes longer depending on the patient’s ability to tolerate the food. Once maintenance dosing is achieved, we would typically maintain daily dosing for at least 1-2 years, after which we may be able to decrease this to 2-3 times per week. In most cases, you would need to maintain regular exposure for the rest of your life in order to prevent a return of allergic symptoms.
Besides allergic reactions, are there any other side effects of OIT?
Yes, studies suggest that a small percentage of patients receiving OIT develop eosinophilic oesophagitis (EoE), a chronic inflammatory condition of the oesophagus (feeding tube) which can cause difficulty swallowing, food impactions, vomiting, or stomach pain. This usually resolves after stopping the OIT, and there are even some cases where this is a temporary phenomenon that can be treated medically while continuing OIT. Diagnosing EoE can be a bit tricky, because currently this can only be confirmed by endoscopy and mucosal biopsies with a gastroenterologist, which we would help facilitate if necessary.
I already have a diagnosis of EoE, can I still undergo OIT?
This is a fascinating question, and the answer is certainly evolving. If your EoE is very stable and well-controlled, it is absolutely possible to consider OIT to help protect against anaphylaxis, however it is also possible the OIT will trigger a worsening of your EoE. This may result in more frequent need for endoscopy, and potentially more medical treatment for your EoE. Again, these issues need to be factored into the shared decision-making process with your allergist.
If I am not ready to do OIT, what are my treatment options?
The current standard of care for food allergy is to avoid the food as strictly as possible, and be prepared to treat any reactions that may occur from accidental exposures. We will review the details of your BSACI Allergy Action Plan whether or not your chose to undergo OIT, and these allergies will be revisited on a regular basis as always. If you change your mind later, that will lead to another conversation on the issue!
I tried OIT before, but was unable to continue because of adverse reactions. Can I try again?
Things can change. We are not the same people we were in the past or will be in the future, and our allergies also change over time. There are many reasons OIT may not work out for someone, and those may also fluctuate. Additionally, it is possible that a different OIT protocol was not right for you, or it may be reasonable to consider trying Xolair to help facilitate the OIT. Regardless, this is simply another conversation to have and explore your options!
Do you accept insurance, and will my insurance cover OIT?
We are not aware of any UK based insurance policies that cover any allergy treatment and so would not expect this to be covered. A separate document will be provided relating to costs.