Cow Milk Protein Allergy
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Direct answer
Cow milk protein allergy is an immune reaction to proteins in cow's milk, mainly casein and whey, and it may be IgE-mediated, non-IgE-mediated or mixed. Its features range from urticaria and anaphylaxis to repetitive vomiting and blood in the stool. Management is complete avoidance of cow's milk protein, with an extensively hydrolysed or amino acid formula for formula-fed infants and a maternal elimination diet for breastfed infants.
What you must remember
- IgE-mediated: immediate reactions within minutes to two hours, such as urticaria, angioedema, vomiting, wheeze and anaphylaxis, supported by skin prick or specific IgE testing.
- FPIES: a non-IgE reaction with repetitive vomiting 1 to 4 hours after ingestion, lethargy, pallor and dehydration, and occasionally shock.
- FPIAP: non-IgE proctocolitis in otherwise well infants, usually under six months, with blood and mucus in the stools, often in exclusively breastfed babies.
- Lactose intolerance: a sugar intolerance from lactase deficiency or injury, which is not immune-mediated and does not cause urticaria or anaphylaxis.
- Formula choice: an extensively hydrolysed formula is generally first line for formula-fed infants with mild to moderate allergy; amino acid formula is used for severe disease or failure of a hydrolysate.
- Soy formula: generally avoided under six months, given cross-reactivity and nutritional concerns in infants.
- Natural history: many children acquire tolerance in early childhood, and reintroduction is done under supervision, often with an oral food challenge.
Three presentations, three mechanisms
A six-week-old exclusively breastfed infant has blood-streaked stools but is otherwise well and gaining weight. The timing and pattern of symptoms decide which category fits, and the comparison below is the usual exam framework.
| Feature | IgE-mediated | FPIES (non-IgE) | FPIAP (non-IgE) |
|---|---|---|---|
| Onset after milk | Minutes to 2 hours | 1 to 4 hours | Days to weeks, usually early infancy |
| Typical features | Urticaria, vomiting, wheeze, anaphylaxis | Repetitive vomiting, lethargy, pallor | Blood and mucus in stools in a well infant |
| Diagnosis | Skin prick or specific IgE | Clinical history and supervised challenge | Clinical; response to elimination |
The same protein can cause very different reactions, so timing and pattern decide the category. Diagnosis of the non-IgE forms rests on the clinical course and response to elimination, not on laboratory tests. Acute FPIES with marked dehydration needs prompt intravenous fluids, because antihistamines do not treat it. Most infants with FPIAP are well and gaining weight, which is why the condition is often mislabelled as infective colitis.
Where the exam tries to catch you
Stems usually test whether a reaction is immune, enzymatic, or a substitution error.
- Trap: calling every milk-related problem an allergy, or every bloating episode lactose intolerance. Correct: cow milk protein allergy is immune and protein-driven, whereas lactose intolerance is enzymatic and does not cause urticaria or anaphylaxis.
- Trap: substituting goat or sheep milk for cow milk. Correct: their proteins cross-react with cow milk proteins, so a child with cow milk allergy can react to them.
- Trap: expecting skin prick tests to diagnose FPIAP. Correct: FPIAP is non-IgE, so tests are usually negative, and the diagnosis rests on symptoms and a response to elimination.
- Trap: treating anaphylaxis with antihistamines alone. Correct: intramuscular adrenaline is first-line treatment for anaphylaxis, and antihistamines are only adjuncts.
Frequently asked questions
How does FPIES differ from IgE-mediated cow milk allergy?
FPIES is a non-IgE reaction causing repetitive vomiting 1 to 4 hours after cow milk, often with lethargy and dehydration. IgE-mediated allergy causes immediate reactions such as urticaria, wheeze or anaphylaxis, and skin prick or specific IgE tests can support that diagnosis.
Which formula is used for infants with cow milk protein allergy?
Extensively hydrolysed formula is generally the first choice for formula-fed infants with mild to moderate allergy. Amino acid formula is reserved for severe disease or when a hydrolysed formula fails.
What should a breastfeeding mother do if her infant has FPIAP?
She removes cow milk protein from her own diet, which usually includes other dairy, and watches the infant's response over a few weeks. Her calcium and vitamin D intake should be maintained through other sources, ideally with dietary advice.
Can a child with cow milk allergy take goat milk?
No. Goat milk is not a safe substitute because its proteins cross-react with cow milk proteins. Children with cow milk allergy need a hydrolysed or amino acid formula, or a dietitian-planned alternative.
Do children outgrow cow milk allergy?
Many children outgrow cow milk allergy during early childhood, though timing varies by type. Reintroduction should be done under medical supervision, often with an oral food challenge, rather than at home.