Sesame Oral Immunotherapy (OIT)

Oral Desensitisation (OD), also known as Oral Tolerance Induction (OTI or OIT) or Food Desensitisation, is a treatment that involves giving very small, but gradually increasing, amounts of the food that the child is allergic to. The intention of OIT is to increase the tolerance to the allergenic food so that larger amounts of the food can be consumed without causing any symptoms and, as a result, accidental exposures to small amounts of allergen should not cause reactions. This treatment has been most studied most extensively for milk, egg and peanut and in early 2020, Palforzia, a peanut containing capsule, become the first licenced food immunotherapy treatment in the US, later receiving a UK market authorisation from the MHRA in October 2021 and was approved by NICE in Feb 2022 for children aged 4-17. The Allergy Centre of Excellence is the largest provider of Palforzia in Europe.

It is important to recognise that this type of treatment leads to a state of desensitisation (a temporary state, where greater amounts of an allergen can be tolerated without symptoms) and not necessarily true ‘tolerance’ (a permanent state where any amount of an allergen can be consumed without any risk of reaction). In practice, this means that the treatment is not a cure but doses of allergen must be continued regularly in the long term for the treatment effect to remain. If it isn’t, the risk of reaction returns. Whilst desensitisation can markedly increase the threshold at which reactions may occur, exposure to larger quantities may still cause a reaction and hence is usually advisable to continue to carry emergency medication, even after successful desensitisation.

Sesame desensitisation is not suitable for all children with sesame allergy.

The aim of the treatment is to reduce sensitivity to sesame, resulting in there being less risk of accidental allergic reactions. The basic principle of treatment is regular exposure to a small but increasing amount of sesame allergen. This exposure will firstly happen under direct supervision in one of our safe clinical environments, but then continues at home, whilst on the same dose, for a minimum of two weeks. At that point, again under direct supervision in the clinic, the dose is slightly increased (up-dosing) and the regular daily dosing is continued at a higher dose. Dose escalation MUST only be done under our direct medical supervision.

If the treatment is discontinued, it is very likely that this effect will be lost within a short period of time and your child will remain allergic to sesame.

The treatment carries a risk of severe and potentially life-threatening allergic reactions, so it is critical that you understand this risk, have read the patient information material and have completed the consent form before progressing with the treatment. The risks associated with the treatment decrease with time on treatment. The risk of acute reactions occurring at home can be markedly reduced by adhering to the advice and training which will be provided by our team.

You can stop the treatment at any time, but your child will have to resume complete avoidance of sesame.

While considerable differences exist between clinical protocols, the desensitisation (immunotherapy) process is conceptually similar. Patients are selected based on a definite diagnosis of sesame seed allergy, usually based on a previous allergic reaction and confirmed by positive allergy tests (Skin Prick Tests and/or Specific IgE blood tests). A diagnostic sesame oral food challenge is not usually needed to make this diagnosis but will occasionally be necessary.

Once it is clear that you fully understand what desensitisation involves, consent forms will be signed and treatment with sesame desensitisation may commence. Normally this begins in the form of sesame flour which is provided in capsules. In higher doses under the sesame desensitisation programme, tahini is used. The sesame desensitisation regimen has been well studied and entails an initiation visit followed by 7 further up dosing visits and then an undefined period of time on maintenance therapy. The IDE and up dosing visits are undertaken in the clinic under supervision whilst the doses between these visits (i.e. the majority of doses) are taken at home. Ultimately, the patient reaches a maintenance dose, for Sesame desensitisation, this is 280mg of sesame protein (approximately 1.0 ml of tahini ). It is anticipated that this level of daily tolerance will protect against accidental ingestion of sesame in every day life although after a period of one year on this daily maintenance dose, a food challenge can be performed to demonstrate how much more sesame can be tolerated.

This protocol typically involves 8 visits although more may be required. In a Canadian study of 270 children using a similar protocol for peanut OIT, 90% reached the maintenance dose. 10 patients (3.7%) had a reaction that required an adrenaline injection. A total of 12 doses caused reactions requiring adrenaline out of a total of 41,020 doses given (0.029%).

Over the past decade there has been a large increase in the number of research studies looking into desensitisation and these have included careful observation of how the treatment impacts on the immune system. It appears that regular exposure to the food causing allergy, but at a level below that which causes a reaction, causes the immune system to increase production of a specific antibody called IgG4. This has a blocking effect on the allergic antibody, known as IgE, and enhances tolerance to the food. As IgG4 levels increase, the effect is greater, allowing more of the food to be tolerated. We are still in the infancy of our understanding as to what is really happening at a molecular level but the science is advancing and we hope that soon there will be a simple blood test that will directly guide desensitisation. However, until we have such a ‘biomarker’ desensitisation is very much led by how well the patient is tolerating food and slowly increasing the level of exposure, rather than anything being gained by lots of blood tests.

Your Allergist will need to refer you to the Allergy Centre of Excellence once a firm diagnosis of sesame allergy has been made. A process of informed consent will then commence prior to the initiation of treatment.

Sesame desensitisation requires 8 clinic visits, over approximately 5 months, to reach a stable state, taking maintenance on the 280mg dose. Sesame in the form of tahini (1.0ml) at maintenance doses will need to be continued until at least the end of the first year of treatment and then options for continued sesame exposure will be discussed

Once you have achieved a stable state of maintenance for 4 weeks, you will be discharged from the Allergy Centre of Excellence and your care will then return to your referring Allergist; together you could decide if an oral challenge is required to ascertain how much sesame is tolerated if higher amounts are eaten.

Potential risks of the desensitisation programme need to be weighed up with the benefits. It is likely that your child will experience some allergic symptoms during the programme. These symptoms are likely to be minor e.g. hives, lip swelling, vomiting, particularly in preschool children. More severe reactions (anaphylaxis) including wheeze and difficulty breathing may occur but are uncommon. An allergy management plan will be provided so you know what to do if your child suffers an allergic reaction. If your child is unwell with colds, coughs or vomiting bugs, they may be more prone to allergic symptoms. Your child should continue with the amount, but if they do get symptoms then the dose will be reduced before going back up again. You will be carefully briefed as to how to manage these situations and have daily direct access to our team to support any decisions on dosing.

Food desensitisation is not a cure – it induces a temporary state where the patient is less sensitive and if peanut is no longer consumed, the allergy will soon return to its previous state. As we do not know exactly how long children remain tolerant to an allergen if they stop taking the regular dose, we have to assume that children need to continue to eat allergen-containing food indefinitely at least 3 times a week to maintain their tolerance. If you child does not eat the allergen-containing food for more than 2-3 weeks or suffers from an asthma attack requiring oral steroids (prednisolone), then they will need to resume exposure under supervision at a lower dose again. However, as some children will outgrow their allergies, OIT can provide protection until this happens.

Longer term outcomes have been established for peanut; It is hoped that similar long-term outcomes will be enjoyed after completing sesame desensitisation.

For peanut, a recent 5 year follow up study of young children who undertook a similar desensitisation programme to peanut showed that 93% of the children were still consuming regular peanut, often in large quantities, and that only 7% reported any further symptoms of allergic reactions, all of which were minor. 90% of patients reported an improvement in lifestyle quality for themselves and their perception of that of their child (Herlihy et al, JACI 2020).

A follow-up study of children who had undergone the Canadian OIT protocol that we use, showed that about 78.6% of pre-schoolers on 300mg peanut oral immunotherapy maintenance for 1 year had a negative cumulative 4000-mg (approx. 16 peanuts) oral food challenge without symptoms, and 98.3% could tolerate greater than or equal to 1000 mg (approx. 4 peanuts), which importantly would be sufficient to protect against accidental exposures (Soller et al, JACI-In practice 2020)

Patients have typically been excluded from studies if they have experienced a recent life-threatening allergic reaction, poorly controlled asthma, suspicion of eosinophilic gastrointestinal disease, or other factors that would hinder their ability to cooperate with the treatment e.g. a high level of personal or family member anxiety. Patients who are over the age of 17 years are not eligible for this treatment.

Even if your child is suitable for immunotherapy, it does not mean that it is the right treatment for them. For many patients, continuing to avoid peanut, coupled with an appropriate emergency action plan is the right way to manage the allergy; indeed, this is the default management course for nearly all sesame allergic patients in the world. Desensitisation carries a risk and also has an impact on your day-to-day life during the updosing period and beyond. If your child is medically suitable, there is an important process of shared decision making, alongside detailed information about the treatment, to help you decide if it is the right thing to do. We will not consider your child for treatment without going through this process and you will be required to sign a consent form to confirm that you have discussed the pros and cons of each approach.

If your child is unable to tolerate the therapy a discussion will be had with the team with respect to continuing on therapy. There are many reasons for not being able to tolerate the therapy or the issue may be one of logistics. If allergic side effects are the issue, then we will discuss reducing the dose and prolonging the up-dosing schedule, as well as the use of concomitant medications such as antacids, and anti-histamines. If the difficulty is with taste, our expert dietitian and nursing team will have tips to assist with this. If the side effect is that of eosinophilic oesophagitis (EoE), therapy will be stopped. We will endeavour to circumvent logistical concerns by offering clinic visits on multiple days of the week running into the early evening.

Oral desensitisation has been best studied for peanut allergy. Studies that included adults were less successful at enrolling and reacting adult participants, some of the difficulty relates to the logistical demands of such a program but it increasingly believed that adverse reactions are more common with increasing age. Adult patients are also more adept at dietary avoidance as compared to younger children where trust must often be placed in people catering for your child.

The safety and efficacy for use in children 1-4 years of age has been trialled in the Artemis 005 peanut and the early released results find that efficacy and safety profile is at least as favourable as in older children.

The Allergy Centre of Excellence offers sesame desensitisation in children aged 17 years and below.

The cost of oral immunotherapy to sesame costs £6,000. If you are eligible to start multi OIT (two allergens at the same time), the price is £9,600. Your referring consultant will assess whether multi OIT is an option for your child. Unfortunately, it is unlikely that insurance will cover the cost of the treatment. However, we can offer payment plans which allow you to spread the cost.