D2.296 - Heat-Stable Egg Allergens in a Patient With Severe Reactions to Cooked and Raw Hen’s Egg

Hen’s egg allergy commonly presents in childhood and is usually dominated by reactions to ovomucoid and ovalbumin. Heat processing typically reduces allergenicity, allowing many egg-allergic individuals to tolerate cooked or baked egg. However, a subset of patients shows persistent reactivity to heated egg proteins, suggesting sensitization to heat-stable components. Molecular analysis is essential to determine the specific allergens that remain active after cooking.

A 52-year-old woman reported respiratory discomfort during egg cooking and gastrointestinal and systemic symptoms after ingestion of raw and lightly cooked egg, including an anaphylactic reaction to raw whole egg. She avoided egg thereafter, tolerating only trace amounts in baked goods. Clinical evaluation included skin prick testing to egg components, measurement of total IgE and specific IgE to whole egg, egg white, egg yolk, ovalbumin and ovomucoid, and baseline tryptase.Protein extracts were prepared from raw whole egg, raw yolk, raw egg white, cooked whole egg and baked egg (200 °C). Protein profiles were analyzed by SDS-PAGE, and IgE-binding patterns were assessed by IgE–Western blot using the patient’s serum.

Specific IgE testing showed elevated IgE to whole egg (80.4 kU/L), egg white (94 kU/L), egg yolk (71.4 kU/L), ovalbumin (72.9 kU/L) and ovomucoid (>100 kU/L), with a total IgE of 359 kU/L. SDS-PAGE demonstrated distinct bands corresponding to major egg proteins in all extracts. IgE–Western blot revealed consistent IgE binding to a ~45 kDa band compatible with ovalbumin and to a 25–30 kDa band compatible with ovomucoid in raw whole egg, raw egg white, cooked whole egg and baked egg. An additional ~100 kDa band was recognized in raw egg white. Reactivity persisted across cooked and baked extracts, indicating that the patient’s sensitization involves heat-stable epitopes.

The patient exhibits strong sensitization to major egg white proteins, with molecular evidence of IgE recognition of ovomucoid and partially heat-resistant ovalbumin across raw, cooked and baked egg. This profile explains her persistent clinical reactivity to heated egg and highlights the diagnostic value of IgE–Western blot in identifying heat-stable egg allergens in adults with severe egg allergy.