Peanut, tree-nut and seed allergy — formative SAQs

SAQ 1 (10 marks)

A 5-year-old boy with known peanut allergy and asthma develops facial urticaria, wheeze and abdominal pain within five minutes of eating a biscuit at a birthday party. His mother gives an antihistamine. Fifteen minutes later he is pale and drowsy with stridor. [12]

1. State your diagnosis and give the immediate pharmacological treatment, including dose, route and site. (3) [12]
2. List four adjuncts to the first-line agent and the correct positioning for this child. (3) [12]
3. Explain why asthma increases this child's risk of a fatal reaction and state the observation period you would recommend after recovery. (4) [12]

Model answer — SAQ 1

1. Anaphylaxis. The immediate treatment is intramuscular adrenaline into the anterolateral thigh (vastus lateralis), at approximately 0.01 mg/kg, repeated every five minutes if features persist; the antihistamine was an inappropriate first step and delayed definitive treatment. [12]

2. Adjuncts include high-flow oxygen, intravenous fluid boluses for shock, nebulised salbutamol for persistent bronchospasm, and an H1 antihistamine for urticaria. Position the child supine with legs elevated (left lateral if vomiting), because sitting a shocked child up can be fatal. [12]

3. Uncontrolled asthma is the strongest comorbid predictor of fatal food-induced anaphylaxis, both by compounding respiratory compromise and by reflecting undertreated airway inflammation. He requires a prolonged period of observation for biphasic recurrence — at least four to six hours, and admission if severe features or poor asthma control persist — and a plan review including two autoinjectors. [12]

SAQ 2 (10 marks)

A 4-month-old infant has severe eczema and a known egg allergy. The parents ask whether to avoid giving peanut. [1]

1. Summarise the evidence that supports a specific feeding recommendation for this infant, including the magnitude of the effect. (4) [1]
2. Outline the practical diagnostic and feeding pathway you would recommend, referencing your local guideline. (3) [1]
3. The same parents later ask whether a positive peanut skin-prick test means their child is definitely allergic. Explain the distinction between sensitisation and clinical allergy and how you would resolve uncertainty. (3) [3]

Model answer — SAQ 2

1. The LEAP trial randomised high-risk infants (severe eczema and/or egg allergy) to sustained peanut consumption versus avoidance from 4 to 11 months, and found roughly an 80 per cent reduction in peanut allergy at age 5 in the consumption group. This overturned prior advice to delay allergenic foods and established early, sustained introduction as prevention in high-risk infants. [1]

2. Per the NIAID addendum and ASCIA guidance, I would arrange peanut-specific IgE or skin-prick testing in this high-risk infant, introduce age-appropriate peanut (such as smooth peanut butter or peanut flour) from four to six months under supervision if testing is negative or low, and maintain regular consumption. A strongly positive test or a reaction prompts specialist review and, where indicated, a supervised introduction or challenge. [1]

3. A positive skin-prick or specific IgE result indicates sensitisation, not clinical allergy, because many sensitised children tolerate the food. I would interpret the result in the light of the history and, where uncertainty persists, arrange a supervised oral food challenge — the gold standard — to confirm or exclude true allergy before imposing lifelong avoidance. [3]