Egg, wheat, soy, fish and shellfish allergy: SAQ

This child has IgE-mediated egg allergy. Her history of moderate eczema, a reproducible immediate reaction (urticaria, angioedema and vomiting within twenty minutes) to scrambled egg, a skin-prick test of 5 mm and an egg-white specific IgE of 8 kU/L together meet the clinical and investigative criteria for egg allergy. The broad elimination diet her parents have adopted is not justified, because the other foods have not been shown to be allergic, and a confirmed allergy to one food does not imply allergy to the others. She needs a focused plan and the restoration of non-allergenic foods. [1]

Question 1 (10 marks)

Classify her reaction, justify the diagnosis, and outline the immediate management plan including dietary advice. (4 marks for classification and diagnosis; 3 marks for the management plan; 3 marks for dietary advice and correcting the elimination diet.) [2]

Her reaction is IgE-mediated, distinguished from non-IgE reactions by its rapid onset within minutes to two hours of exposure and its immediate phenotype of urticaria, angioedema and vomiting. The diagnosis is supported by the consistent history, a skin-prick test of 5 mm (above the 3 mm threshold) and a raised egg-white specific IgE of 8 kU/L, all of which indicate sensitisation that, combined with the convincing history, supports clinical egg allergy. The oral food challenge is the gold standard, but in this case the history and tests are sufficiently concordant that the diagnosis is established without challenge, and the priority is the management plan rather than further confirmation. [1]

The immediate management plan has three components. First, allergen avoidance of egg, with dietetic support to read labels for hidden egg (egg as a glaze, binder or in baked goods). Second, a written anaphylaxis action plan (the ASCIA plan in Australasia) and an adrenaline autoinjector, because she has had a systemic reaction; she is under 20 kg so the 0.15 mg device is appropriate. Third, family and carer education in recognising an early reaction and using the autoinjector, with a follow-up allergy appointment. [2]

The dietary advice must correct the over-broad elimination. There is no evidence of wheat, soy, fish or shellfish allergy, and removing them risks nutritional deficiency, growth faltering and unnecessary anxiety. These foods should be reintroduced. Egg remains the only confirmed allergen, and a supervised baked-egg challenge is appropriate, because many egg-allergic children tolerate extensively heated egg in a matrix such as a well-baked muffin, and regular baked-egg consumption can accelerate tolerance. A dietitian should oversee the reintroduction of the other foods and the baked-egg ladder. [1]

Question 2 (10 marks)

Describe the natural history of egg allergy and the role of component-resolved diagnostics and the baked-egg ladder, and give the safety-netting advice to the family. (4 marks for natural history and predictors; 3 marks for component diagnostics and baked-egg; 3 marks for safety-netting.) [3]

The natural history of egg allergy is one of progressive resolution in about half of children. The HealthNuts population-based longitudinal study found that roughly half of challenge-confirmed egg allergy at age one had resolved by age six, and that resolution is faster in children who tolerate baked egg early. The predictors of persistence are a larger skin-prick wheal, a higher egg-white specific IgE and, in particular, a high ovomucoid (Gal d 1) specific IgE, because ovomucoid is heat-stable and its recognition marks the baked-egg-reactive, slower-to-resolve phenotype. [3]

Component-resolved diagnostics refine the prognosis and the plan. Measuring ovomucoid-specific IgE tells the clinician whether the child is likely to tolerate baked egg: a low ovomucoid IgE with a positive ovalbumin suggests heat-labile, baked-egg-tolerant allergy, whereas a high ovomucoid IgE predicts baked-egg reactivity and persistence. The baked-egg ladder then introduces extensively heated egg in a matrix under supervision, and if tolerated, the child consumes it regularly to build tolerance, advancing toward less-heated forms over months. This is the active-tolerance pillar of modern egg-allergy management. [1]

The safety-netting advice to the family is specific, written and behaviour-based. The parents are told that their daughter is allergic to egg only, that most children outgrow it so re-testing each year is appropriate, and that the other foods should return to her diet. They must carry the adrenaline autoinjector and know the ASCIA action plan, and they should call an ambulance and use the autoinjector at the first sign of any breathing difficulty, fainting or collapse after a food exposure. Because she has eczema and the family has demonstrated a tendency to over-restrict, the follow-up appointment should explicitly review the diet and the plan, and a school or childcare plan should be put in place. [2]