Cow’s Milk Protein Allergy

Cow’s milk protein allergy is a condition typically affecting infants and young children under 3 years. It involves hypersensitivity to the protein in cow’s milk. This may be IgE mediated, in which case there is a rapid reaction to cow’s milk, occurring within 2 hours of ingestion. It can also be non-IgE medicated, with reactions occurring slowly over several days. 

This is different to lactose intolerance and cow’s milk intolerance. People with cow’s milk protein allergy do not have an allergy to lactose. Lactose is a sugar, not a protein. Cow’s milk intolerance is not an allergic process and does not involve the immune system.

Cow’s milk protein allergy is more common in formula fed babies and those with a personal or family history of other atopic conditions.



Cow’s milk protein allergy usually presents before 1 year of age. It may become apparent when weaned from breast milk to formula milk or food containing milk. It can present in breastfed babies when the mother is consuming dairy products.

Gastrointestinal symptoms:

  • Bloating and wind
  • Abdominal pain
  • Diarrhoea
  • Vomiting

General allergic symptoms in response to the cow’s milk protein:

  • Urticarial rash (hives)
  • Angio-oedema (facial swelling)
  • Cough or wheeze
  • Sneezing
  • Watery eyes
  • Eczema

Rarely in severe cases anaphylaxis can occur.



The diagnosis is made based on a full history and examination. Skin prick testing can help support the diagnosis but is not always necessary. Avoiding cow’s milk should fully resolve symptoms:

  • Breast feeding mothers should avoid dairy products
  • Replace formula with special hydrolysed formulas designed for cow’s milk allergy

Hydrolysed formulas contain cow’s milk, however the proteins have been broken down so that they no longer trigger an immune response. In severe cases infants may require elemental formulas made of basic amino acids (e.g. neocate).

Most children will outgrow cow’s milk protein allergy by age 3, often earlier.

Every 6 months or so, infants can be tried on the first step of the milk ladder (e.g. malted milk biscuits) and then slowly progress up the ladder until they develop symptoms. Over time they should gradually be able to progress towards a normal diet containing milk.


Cow’s Milk Intolerance versus Cow’s Milk Allergy

Cow’s milk intolerance is different from cow’s milk protein allergy. It is important not to get these mixed up. Cow’s milk intolerance presents with the same gastrointestinal symptoms as cow’s milk allergy (bloating, wind, diarrhoea and vomiting), however it does not give the allergic features (rash, angio-oedema, sneezing and coughing).

Infants with cow’s milk allergy will not be able to tolerate cow’s milk at all, as it causes an allergic reaction, whereas infants with cow’s milk intolerance will be able to tolerate and continue to grow and develop, but will suffer with gastrointestinal symptoms whilst having cow’s milk.

Infants with cow’s milk intolerance will grow out of it by 2 – 3 years. They can be fed with breast milk, hydrolysed formulas and weaned to foods not containing cow’s milk. After one year of age they can be started on the milk ladder.


Last updated January 2020