Cow’s milk protein allergy occurs when the immune system reacts to proteins in cow’s milk. It mainly affects infants and young children. It is different from lactose intolerance, which is difficulty digesting the milk sugar lactose.
Symptoms
Immediate reactions can begin within minutes or up to about two hours and may include hives, swelling, vomiting, coughing, wheezing or breathing difficulty. Delayed reactions may develop over several hours or days and can include eczema, reflux, vomiting, diarrhea, constipation, blood or mucus in stools, feeding difficulty or poor growth.
When to Get Emergency Help
Contact your local emergency services immediately for swelling of the tongue or throat, breathing difficulty, collapse, severe dizziness or loss of consciousness. Use a prescribed epinephrine auto-injector according to the child’s emergency plan and device instructions.
Diagnosis
Diagnosis begins with a detailed allergy history. Skin prick testing or specific IgE blood tests may help when an immediate allergy is suspected. Delayed allergy is often assessed with a planned period of milk exclusion followed by reintroduction under professional guidance. Testing and reintroduction should be individualized.
Feeding and Treatment
Treatment involves avoiding cow’s milk protein while maintaining adequate nutrition. Infants who need formula may require a specialist hypoallergenic formula. Ordinary lactose-free formula is not suitable for cow’s milk protein allergy because it can still contain milk protein. A healthcare professional or registered dietitian can advise on suitable alternatives and when reintroduction may be appropriate.
Do not remove dairy from a breastfeeding parent’s or child’s diet without professional advice. Milk products provide important nutrients, and an appropriate replacement plan may be needed.
Related topics
Sources and Further Reading
Last reviewed: 4 September 2026. This page provides general health information and does not replace individual medical assessment or treatment.