Trends and patterns among egg-allergic children in Hong Kong: A retrospective cohort study

Background: Adverse reactions upon hen’s egg (HE) consumption may be classified into intolerance or allergy, with the latter further classified into suspected egg allergy (SEA), probable egg allergy (PEA) or confirmed egg allergy (CEA) depending on clinical symptomatology and onset timing. HE allergy affects a significant proportion of children worldwide, yet the clinicodemographic profiles of each subgroup remain unknown. Objectives: We aimed to describe clinical features, sensitization patterns, and temporal characteristics of subgroups among suspected egg-allergic children. Methods: Children (aged <18 years) with clinically SEA who presented from 1999 to 2024 at a university-affiliated pediatric unit in Hong Kong were included. Categorical and continuous variables were analyzed by Fisher’s exact test and Mann–Whitney U test. Intergroup age ranges and SPT wheal diameters were compared with the Kruskal–Wallis test and Dunn’s multiple comparisons post hoc test. Results: A total of 207 (55.5%) out of 373 included patients were deemed PEA by history, among whom 173 were CEA; the remaining 166 were “unlikely egg-allergic” UEA. Around 60% of subjects in the CEA, PEA-not-CEA, and UEA subgroups had comorbid eczema. Well-cooked HE was the predominant food trigger for all subgroups, and the differential allergenicity of preceding triggers did not correlate with the severity of allergic reactions. Patients in the PEA-not-CEA subgroup were significantly older than those from the UEA or CEA subgroups ( P < 0.001). The number of newly attended suspected, probable, and confirmed egg-allergic cases showed a 2-fold increase from 2000–2004 to 2020–2024, although not statistically significant. Conclusion: Younger age at first visit correlates with a greater likelihood of true HE allergy among PEA children. “Probably egg-allergic” status is associated with dyspnoea, while UEA status correlates with generalized or localized nonurticarial rash as well as eczema flare. Some UEA children may show positive egg-specific sensitization, so it is critical to review patients’ clinical history before proceeding with tests.