Short answer
Egg allergy can cause hives, swelling, vomiting, abdominal symptoms, cough, wheeze or breathing difficulty. Reactions vary and can be serious; suspected allergy requires qualified medical assessment.
Allergy is an immune reaction
Symptoms often appear soon after eating egg but timing and severity vary. A person may react to small amounts, baked egg or raw egg differently. Previous mild reactions do not guarantee that a future reaction will also be mild.
When to seek urgent help
Difficulty breathing, collapse, marked dizziness or swelling of the mouth, tongue or throat can indicate anaphylaxis and needs urgent emergency treatment. Follow an existing allergy action plan and use prescribed adrenaline promptly when instructed.
Diagnosis and everyday management
Do not use unsupervised food challenges to diagnose allergy. A clinician may combine the reaction history with tests and, when appropriate, a supervised food challenge. Ingredient labels, cross-contact and vaccination or medication questions should be addressed with local professionals.