Comprehensive Review of Current Knowledge on Egg Oral Immunotherapy

Oral immunotherapy (OIT) is an attractive strategy for active treatment of IgE-mediated food allergy. Multiple egg OIT studies have been published to date, but many are uncontrolled. Furthermore, interpretation of the results is difficult because of significant heterogeneity in design, aims, and population. Most studies have demonstrated the potential of egg OIT to induce desensitization, albeit to different extents (0%-100% of patients). However, few studies have explored the capacity of OIT to maintain tolerance, that is, enabling the patient to continue consuming egg after suspension of therapy. Nowadays, 28% to 75% of patients maintain tolerance after 1 to 3 months of their elimination diet. Adverse effects are the main drawback of this treatment, which is still not recommended in routine practice. Adverse reactions are not reported homogeneously, with the result that it is difficult to properly assess outcomes. The overall impression is that adverse reactions affect most patients and tend to be frequent, although of mild to moderate severity. Nevertheless, severe events such as anaphylaxis or eosinophilic esophagitis may also occur. Immunological changes resulting from egg OIT, for example, the decrease in the size of the skin prick test wheal and the levels of egg white sIgE and a significant early increase in egg white sIgG4, have been reported. Several areas of egg OIT remain unclear, including patient selection, materials used, dosing schedule, treatment duration, long-term maintained effectiveness, requirements for implementation in clinical practice, influence on quality of life, and cost-effectiveness of treatment. In this review, we provide an in-depth examination of methodological differences between studies in order to understand the diversity in the efficacy and safety results of the procedures used in egg OIT.