Food allergy is common, affecting 5% of UK children and can cause severe allergic reactions. Every year, children have accidental exposures to the foods they are allergic to and whilst most reactions are mild, occasionally, they can be more severe. Until recently, the only treatment for food allergy has been careful avoidance. This is starting to change and there has now been a 15 year history of intensive medical research into desensitisation to common food allergens, such as peanut, milk and egg, which means that in some cases, there may be other approaches to treatment.
What is food desensitisation?
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 amount of the food that the child is allergic to. The intention of this is to increase the tolerance to the food allergen so that larger amounts of it can be taken without causing any symptoms and as a result, allergen containing foods can be eaten safely or at very least, accidental exposures to small amounts of them will not cause reactions.
This treatment has been most studied for peanut, milk and egg. It is important to recognise that this treatment leads to a state of desensitisation (a temporary state, where greater amounts of allergen can be tolerated without symptoms) and not necessarily true ‘tolerance’ (a permanent state where any amount of the allergen can be consumed without any risk of reaction). In practice, this means that the regular doses of allergen must be continued regularly in the long term for the treatment effect to remain.
This treatment is thus not a cure and if doses of the allergen are not continued regularly, the risk of reaction returns.
What does food desensitisation involve?
The starting point is an assessment visit, to discuss the process and ensure that you fully understand it. The assessment will involve a detailed history and examination focussing on the relevant food allergy and may require skin prick or blood tests if these have not been done for more than 6-12 months. It will also require a detailed asthma assessment and where appropriate, lung function testing as any child whose asthma is not extremely well controlled, would not be suitable for treatment.
If it is felt your child is suitable for the treatment, you will be asked to sign a consent form to indicate that you have fully understood the risks involved. You will be prescribed an Epipen and trained in its use, if this hasn’t been done already. In the case of milk or egg allergy, if your child has never been exposed to baked milk or baked egg, it may be necessary to clarify if your child is able to tolerate this, by consuming a fairy cake under supervision. If they can, this suggests a different strategy for desensitisation may be used but if your child cannot tolerate milk/egg in the baked form, and is otherwise suitable, then the treatment can proceed.
Treatment starts with a tiny amount of allergen being given under medical supervision. You will be shown how to make up the correct doses in order for the same dose to be given safely at home. Depending on the allergen and the protocol, you will then either slowly increase the dose at home or, for example with peanut, just give the same dose, returning intermittently to give an increased dose under direct medical supervision. You will be supported, with close email contact throughout the process.
How long does the food desensitisation process take?
This will depend on the protocol use and the success of the treatment. With peanut, it may take approximately 4-6 months to get to the ‘maintenance’ dose but it is important to note that this can be slowed down, with ‘up dosing’ visits where higher doses are carefully trialled, may be done at longer intervals if preferred. If a child has a lot of reactions, this may also slow the process down. The important thing is that safety is more important than how quickly the process is done.
How does Food Desensitisation work?
Studies on desensitisation suggest that exposure to the allergic at doses that do not cause reactions, promotes the production of food specific IgG4 antibodies and reduces food specific IgE. This gradually tips the balance towards tolerance rather than allergy, at least while the levels are maintained.
What allergies does Food Desensitisation work for?
Most research is focussed on milk, egg and peanut and these are the allergens most commonly desensitised. However, there is increasing interest in desensitisation to treenuts, sesame and other foods although safety data from safety studies remains lacking.
Does Food Desensitisation have any side effects?
The key symptoms are those of allergic reactions to the doses given – these are usually mild (itch, rash, hives as well as gastrointestinal symptoms such as abdominal pain). More severe reactions are rare but can happy including anaphylaxis. The risk of this will vary according to the allergen. Studies relating to 1127 patients receiving Palforzia (peanut) in children age 4 to 17, 14 patients (1.2%) had a severe reaction, all of which responded to emergency treatment with Epipen.
How effective is food desensitisation?
There are numerous studies from around the world as well as systematic reviews (where the results of lots of studies are combined) that demonstrate that OIT works well for peanut, milk and egg. Different studies use different approaches, in different children but report up to 100% effectiveness.
Children tend to have 3 possible responses to treatment:
- they achieve a full, high dose that they can tolerate without any problem
- they can’t reach the full dose without persistent side effects but can still tolerate a useful amount of allergen without reactions
- they are unable to progress at all due to side effects. Studies are starting to show that children with very high skin prick or blood allergy tests to the allergen may be more likely to have side effects during the treatment and this will be considered at any assessment.
Multiple studies have also shown a clear improvement in quality of life for both children and parents, where OIT has been performed.
How safe is food desensitisation?
There has been a lot of concern around safety of this treatment, because of the known risk of severe allergic reactions that could happen to foods. Most, if not all children, will have some allergic reactions during the treatment but these are virtually all mild. Typical reactions are rashes, lip/face swelling, wheeze and abdominal discomfort. Severe reactions, requiring adrenaline are reported in a small number of patients in the published studies but with this treatment now widespread in Europe and the US, it is very reassuring that there have been no reported fatal or near fatal reactions reported. However, there are a number of clear ways that the risk of severe reactions can be reduced and many lessons have been learned for the severe reactions that have occurred. The most important influence on safety is the actual desensitisation protocol. Some studies are focussed on a rapid dose increase, with multiple hospital visits. This can mean the treatment works much more quickly but carries a greater risk of severe reactions. Other protocols are much slower, with much smaller dose increases, far less hospital visits and as a consequence are safer. This balance between speed and safety is a key part of any discussion about the treatment and will very much depend on the individual case. It is impossible to desensitise without any risk of allergic reaction but this is further mitigated by not offering it to certain patients, ensuring parents are fully able to manage allergic reactions in the unlikely event that they happen (patient will be prescribed and trained to use Epipens), and observing some simple rules around dosing. The risk of reacting must also be considered in the context of the risk of severe reactions that may happen if the child were not desensitised and had an accidental exposure.
There is also a concern that OIT can result in the development of eosinophilic oesophagitis (EoE – an inflammatory condition of the oesophagus) and other food-induced gut related problems. A systematic review reported EoE in up to 2.7% of patients undergoing OD for IgE mediated food allergy (although the review is based on incomplete datasets, because most trials of OD have not reported the presence or absence of EoE as a longer-term adverse event) although as EoE is known to disproportionately affect children with allergies anyway, there is no evidence as yet of a causative link.
Currently, international guidelines on the management of food allergy (published in 2018) have stated that OIT to peanut, egg and milk can be offered by allergy specialists, reflecting our improved understanding and the experience of the many doctors in Europe now offering this.
What if food desensitisation doesn’t work?
This treatment does not work for everybody, but if the dose cannot be increased above a certain point because of recurrent side effects, then this dose can be continued for 3 months and then increasing attempted again. This can often be successful. Even if only limited desensitisation is achieved, this can still protect from reactions due to accidental exposures. It is also possible for smaller doses, if required daily for a long period, to be changed to an easier alternative eg chocolate button in milk OIT.
Can I get food desensitisation for my child?
OD is not right for everyone. If your child has suffered severe reactions, especially to very small exposures to milk or has poorly controlled asthma or other illnesses, then this treatment is not suitable.
If your child’s allergy tests are very high then this increases the change of problematic side effects and reduces the chance that the treatment will be successful. If you are unable to commit to very reliable daily dosing then this would not be suitable.
If your absolute priority in managing your child’s food allergy is avoiding any reactions, then a policy of strict avoidance is probably best. If you are prepared to accept a regular daily treatment, with occasional mild allergic reactions then OIT is worth considering.
How much does food desensitisation cost privately?
Cost of treatment will depend on the cost of the allergen itself – which may simply be milk or egg or for children having Palforzia, can be very significant. It will also depend on the number of visits to increase the dose so will depend on the protocol used.
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Professor Adam Fox
Date reviewed: March 2021
Adam Fox is a Professor of Paediatric Allergy with over 20 years experience in both the NHS and private sector. Professor Fox is Commercial Medical Director at Guy’s & St Thomas’ Hospitals NHS Foundation Trust and Professor of Paediatric Allergy at King’s College London and the founding Director of the KCL Allergy Academy, a postgraduate educational programme, which was a finalist at the BMJ Awards in 2018.
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