Cow's-milk protein allergy — formative SAQs

SAQ 1 (10)

A 5-month-old formula-fed infant presents with a 3-week history of blood and mucus in the stools. The infant is well-looking, afebrile, feeding normally, and growing along the 50th centile. There is no vomiting, no rash, and no respiratory symptoms. [1] [2]

1. State the most likely diagnosis and the single investigation you would use to confirm it. (3) [1]
2. Outline your initial management, including the feeding change you would make. (4) [1] [2]
3. Describe the prognosis and the plan you would give the family for reintroduction. (3) [1] [4]

Model answer

Diagnosis and confirmation. The most likely diagnosis is cow's-milk protein-induced proctocolitis, the commonest non-IgE-mediated phenotype of cow's-milk protein allergy, presenting as blood and mucus in the stools of an otherwise well, thriving infant. Confirmation is clinical: I would not order skin-prick or specific IgE, because these are typically negative in non-IgE disease. I would eliminate cow's-milk protein for two to four weeks and confirm the diagnosis by resolution of symptoms, then a planned reintroduction that reproduces them. [1]

Initial management. Switch from standard cow's-milk formula to an extensively hydrolysed formula as first-line. The family should expect the bleeding to settle within two to four weeks. No antibiotics, no invasive investigation, and no restrictive work-up are required in this well-looking, growing infant. I would also assess the family's understanding of what elimination means and arrange dietetic input if there is any concern about nutrition, though an extensively hydrolysed formula is nutritionally complete. [1] [2]

Prognosis and reintroduction. The prognosis is excellent: most infants with proctocolitis tolerate cow's milk by their first birthday. I would plan a structured milk ladder or a planned reintroduction from around nine to twelve months, beginning with baked milk. I would reassure the family that this is a benign, well-looking pattern that needs no invasive tests and that the outlook is resolution, while giving a clear safety-net to return if symptoms recur or growth falters. [1] [4]

SAQ 2 (10)

A 6-month-old infant turns red, develops lip swelling, vomits, and becomes wheezy and floppy within ten minutes of a first bottle of cow's-milk formula. [3]

1. State your immediate priorities and the emergency treatment sequence (no invented drug doses). (4) [3] [5]
2. Explain how you would confirm the diagnosis after the acute episode and why tests alone are insufficient. (3) [3] [1]
3. Outline the discharge plan and the long-term management of the feeding and anaphylaxis risk. (3) [3] [5]

Model answer

Immediate priorities and treatment. This is anaphylaxis: acute skin change (erythema, lip angioedema) plus respiratory compromise (wheeze) and circulatory compromise (floppiness) within minutes of cow's-milk exposure. Immediate priorities are lie the infant flat with legs raised, give intramuscular adrenaline into the anterolateral thigh at the weight-appropriate dose, repeat after five minutes if there is no improvement, and call for paediatric emergency help. I would support the airway, give high-flow oxygen, and start intravenous fluids for shock. The family and any witness need calm, clear communication during resuscitation. [3] [5]

Confirming the diagnosis and why tests alone are insufficient. After recovery I would take a detailed allergy history and arrange skin-prick testing and serum specific IgE to cow's milk to characterise the IgE-mediated phenotype. However, the diagnosis of cow's-milk allergy rests on the clinical reaction to exposure — the child reacted with anaphylaxis, so the diagnosis is established regardless of the test result. Tests phenotype and support; a positive test confirms sensitisation but the reproducible clinical reaction is what makes it allergy. A negative test would not override the history here. [3] [1]

Discharge and long-term plan. Before discharge the infant must have a prescribed adrenaline autoinjector, a written anaphylaxis action plan, caregiver training, and a referral to paediatric allergy. The feeding plan is strict avoidance of all cow's-milk protein, with an amino-acid formula as the substitute given the severity of the reaction and the anaphylaxis risk. The family needs education on hidden milk in processed foods and on cross-contamination. I would plan regular allergy review and a supervised oral food challenge when appropriate to assess tolerance development, since many children outgrow IgE-mediated allergy over time. [3] [5]