D2.05 - Quail Egg Allergy with Independent Hen Egg Sensitization: Insights From Protein Profiling and Inhibition Assays

Egg allergy is typically dominated by sensitization to major hen egg allergens; however, isolated reactions to quail egg have been described and may reflect distinct protein profiles or incomplete cross-reactivity. Molecular analysis is essential in cases where clinical evolution differs from expected tolerance patterns or when cooked forms remain reactive despite standard heating-associated allergen denaturation.

A 10-years old boy, with resolved hen’s egg allergy during early childhood, experienced a reaction to quail´s egg, including perioral erythema, ocular pruritus, pharyngeal itching, eyelid edema, cough and vomiting shortly after handling or ingesting quail egg. After this reaction he developed abdominal pain and vomiting after consuming hen´s egg in certain preparations. Skin prick testing was positive to quail´s egg (raw and cooked) and negative to hen´s egg standard commercial extracts. Specific IgE testing showed sensitization to hen´s egg proteins, including egg white, ovalbumin and ovomucoid, with low or undetectable levels to other foods.Protein extracts were obtained from quail´s egg (whole, yolk, white; raw and cooked) and hen´s egg (whole, yolk, white; raw, cooked, omelette and baked). SDS-PAGE and IgE–Western blot were run under reducing conditions, and an inhibition Western blot evaluated cross-reactivity between quail´s and hen´s egg

Skin testing confirmed sensitization to quail´s egg, and IgE results indicated concurrent sensitization to major hen´s egg allergens. SDS-PAGE revealed similar profiles across quail´s and hen´s egg components, with denaturation-dependent shifts in cooked extracts. IgE–Western blot demonstrated IgE binding to 40 kDa and 25–30 kDa bands in raw quail´s egg whole extract and white, consistent with ovalbumin-like and ovomucoid-like proteins; cooked quail´s egg showed reactivity at 50 kDa and a persistent 25–30 kDa band. Hen´s egg extracts revealed weaker recognition, with bands at 40 and 15 kDa in raw white (likely ovalbumin and lysozyme C) and a predominant 25–30 kDa band in cooked forms which could correspond to ovomucoid.The inhibition assay showed absence of cross-inhibition between quail´s and hen´s egg, confirming co-sensitization rather than cross-reactivity. IgE binding persisted in cooked extracts, indicating heat-stable or partially heat-resistant allergens in both species.

This case demonstrates clinically relevant sensitization to quail´s egg with concurrent but independent sensitization to hen´s egg. Molecular analysis revealed heat-stable or partially heat-resistant proteins driving persistent reactivity and confirmed lack of cross-reactivity between species, which does not explain the loss of tolerance to hen´s egg.