Cow's-milk protein allergy

Synopsis

Recognise immediate and delayed cow's-milk protein allergy, distinguish it from lactose intolerance and common infant symptoms, confirm diagnosis with the appropriate test or elimination-reintroduction sequence, prescribe nutritionally complete substitutes and prevent unsafe restriction or home challenge.

• Cow's-milk protein allergy is immune mediated. Lactose intolerance is not milk allergy and is uncommon as a primary disorder in young infants; lactose-free formula still contains cow's-milk protein.
• IgE-mediated allergy usually produces reproducible symptoms within minutes to 2 hours: urticaria, angioedema, wheeze, cough, vomiting, hypotension or collapse.
• Non-IgE allergy is delayed over hours to days and may cause eczema, diarrhoea, constipation, blood or mucus in stool, vomiting, reflux-like distress or faltering growth; these symptoms are nonspecific.
• First-line diagnosis is an allergy-focused history covering timing, dose, reproducibility, systems involved, feeding, growth, eczema and previous treatment. Do not order indiscriminate food panels.
• For suspected IgE allergy, skin-prick testing or serum specific IgE supports diagnosis only when interpreted against history. Test magnitude does not predict future reaction severity.
• For mild-to-moderate suspected non-IgE allergy, use a 2–6 week cow's-milk protein elimination followed by planned reintroduction. Improvement without relapse on reintroduction does not confirm allergy.
• A medically supervised oral food challenge is the reference standard when diagnosis remains uncertain or specialist reassessment of tolerance is needed; it is not undertaken in primary care for suspected immediate allergy.
• Continue breastfeeding. If symptoms occur through breast milk, a time-limited maternal dairy elimination may be tried with dietitian support, calcium and vitamin D, followed by reintroduction to confirm causality.
• For formula-fed infants, an extensively hydrolysed formula is first line for most mild-to-moderate cases. Use amino-acid formula for severe disease, anaphylaxis, significant faltering or failure of an adequate hydrolysate trial with specialist input.
• Goat's- and sheep's-milk formulas cross-react and are unsuitable. Partially hydrolysed and comfort formulas do not treat allergy; soy is generally avoided under 6 months and needs individual assessment thereafter.
• A home milk ladder is for selected confirmed non-IgE allergy under clinician or dietitian direction. It is unsafe after anaphylaxis or other significant immediate reactions unless the allergy team explicitly plans it.
• Review the diagnosis and test for tolerance. Unnecessary long-term exclusion impairs nutrition, increases cost and may increase anxiety around food.