Background: Over the last few years, studies have shown that the majority of egg allergic children tolerate baked egg (e.g., cake), and that consuming baked egg accelerates the resolution of egg allergy. However, few prospective studies demonstrate the step-wise reintroduction of egg at home after developing baked egg tolerance. Although this could have a positive impact on the children's quality of life and nutrition. Additionally, research supporting the theoretical concept that heating in the presence or absence of wheat causes reduced allergenicity of egg proteins is limited.
Objective: To investigate the clinically most favorable duration of gradual egg-tolerance induction in baked egg tolerant children at home, with regard to complete raw egg tolerance.
Methods: Baked egg tolerant children above 12 months of age were randomly assigned to a short- or long arm protocol. In the short arm, egg-tolerance induction was studied over 18 months compared to 30 months in the long arm. Children were guided through this protocol involving the step-wise introduction of increasingly allergenic forms of egg starting with baked egg offered as cake, followed by hard-boiled egg, omelet/waffle/pancake, soft-boiled egg, and finally raw egg. We hereby designed this protocol based on the influence of thermal processing in the presence or absence of wheat on egg proteins, as investigated by ELISA, SDS-PAGE, and immunoblotting. At inclusion, children either passed an in-hospital cake challenge or had ovomucoid sIgE ≤1.2 kUA/L, which was considered safe for introduction at home.
Results: Gel electrophoresis revealed that the ovalbumin band became weaker with heating, while the ovomucoid band remained stable. In accordance, the IgE-binding to ovalbumin decreased with extensive heating, as opposed to ovomucoid. However, heating in the presence of wheat led to a decreased IgE reactivity to ovomucoid. Of the 78 children in the intention-to-treat group, 39 were randomized to each arm. Fifty-eight children reached the raw egg tolerance endpoint, of which 80% were in the short arm and 69% in the long arm. Within the short arm, the median time to raw egg tolerance was 24 months (95% CI, 21-27 months) compared to 30 months (95% CI, 28-32 months) in the long arm (p = 0.005). No grade IV reactions or cases of eosinophilic esophagitis were observed. The short arm was considered to be non-inferior to the long arm.
Conclusion: Our gradual short arm protocol appears to be safe and allows clinicians to guide baked egg tolerant children toward raw egg tolerance at home. The allergenicity of the egg proteins was affected by heating temperature and duration, as well as the presence of wheat.
Keywords: baked egg; egg allergy; egg ladder; egg oral immunotherapy; egg tolerance; heated egg; ovomucoid sIgE; wheat matrix.
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