Food allergy in childhood: Are we close to having an effective treatment?

Food allergy (FA) has become a growing problem in recent years, particularly among the pediatric population.^1,2 A recent study has moreover emphasized that the “epidemic” has not yet peaked,³ since the number of hospital admissions due to anaphylaxis continue to increase. Food allergy has a strong impact upon the quality of life of the affected patients and their families,^4,5 and can result in nutritional deficiencies secondary to the introduction of restrictive diets.⁶

Food allergy results from failure to develop oral tolerance or from failure of existing tolerance.⁷ A proportion of children with FA will spontaneously overcome the disorder, particularly in the case of allergy to cow's milk and egg – thus indicating that oral tolerance can effectively develop.

At present, the only universally accepted therapeutic option is strict avoidance of the causal food and symptomatic management of the adverse reactions – with special emphasis on the administration of adrenalin in the case of anaphylaxis. However, this approach only reflects the fact that we lack effective etiological treatments, leaving patients vulnerable to the reactions caused by inadvertent ingestion of the causal foods.⁸

The adoption of primary prevention measures allowing the definition and induction of food tolerance mechanisms would be the ideal strategy for reducing the high prevalence of FA.^9,10 Once FA has become established, secondary prevention should ensure necessary avoidance of the allergen until spontaneous tolerance is reached or until tolerance is induced through oral immunotherapy (IOT). Due to the increasing frequency of FA in our pediatric population, we need treatments that are both effective and safe.

Food desensitization protocols or OIT have been used in the last few decades. These strategies involve administration of the causal food, starting with small doses and gradually increasing the dosage as the patient acquires tolerance, with two objectives in mind: (a) to protect the patient against adverse reactions resulting from accidental ingestion of the causal food; and (b) to normalize the diet by achieving specific desensitization to the allergen,¹¹ and ideally securing tolerance or “sustained unresponsiveness”.¹²

The mechanisms of action underlying OIT in FA have not been clearly established, though studies on biomarkers^13–16 indicate that they are very similar to the mechanisms underlying immunotherapy for respiratory allergies.¹⁷

In Spain, as in other countries, a number of centers have been using this new treatment modality, with excellent results. The protocols must always be applied under close supervision by trained professionals, in hospitals where adequate treatment of any serious reactions can be guaranteed. The FA most commonly subjected to OIT is allergy to cow's milk and egg, though studies have also been made with peanut, fish, hazelnut, peach and other foods. The most widely used and documented route is the oral route, though the sublingual, subcutaneous and epicutaneous routes have also been used.

The literature on OIT reports high desensitization indices of between 60% to over 90%, depending on the food involved,^11,18–20 though the frequency of adverse reactions is also high.^21,22 The main problem in evaluating global OIT outcomes is the great variety of protocols used in different countries and centers. Because of this variability it is not possible to establish which are most effective and efficient procedures. Recent reviews and meta-analyses^23–25 have concluded that although OIT is effective, the quality of the evidence is low, due to the heterogeneity of the methods used. Furthermore, while effective, OIT is associated to a high incidence of adverse reactions. The latest review and meta-analysis²⁶ concludes that OIT can be effective in incrementing the reactivity threshold to several foods in patients with IgE-mediated FA, but is also associated to a risk of adverse effects.

This issue of Allergologia et Immunopathologia publishes a document that aims to serve as a clinical guide on the use of OIT in IgE-mediated allergy to cow's milk proteins and egg. It has been jointly developed by members of the Sociedad Española de Inmunología Clínica, Asma y Alergia Pediátrica (SEICAP) and the Sociedad Española de Alergia y Inmunología Clínica (SEAIC).

Based on a review of the literature, and contributing their own experiences, the authors propose a practical guide of use in implementing OIT in both the starting phase and in the maintenance phase. The document seeks to help professionals prescribe treatment schemes that are as homogeneous as possible, and to reduce the incidence of the adverse effects of such treatment. Likewise, models for intervention in cases of poor patient response to the conventional schemes are presented.

We believe that this guide constitutes a good basis for reaching these objectives.

A number of issues remain to be resolved, however:

• 1.

  Is OIT the most effective treatment for achieving food desensitization? Or is it preferable to use other procedures involving different routes and allergens, such as the sublingual route,^27–32 the epicutaneous route,^33–35 modified hypoallergenic molecules,^36–38 OIT with peptides,^39,40 or OIT with heat-modified (baked) foods?^41–48

• 2.

  Is OIT cost-effective and efficient over the long term?

The ultimate aim of the guide is to improve clinical practice and allow the professionals in charge of such treatments to feel that their work is supported by this document.