Written by Dr Nické Theron, Pediatrician.

Cow’s milk protein allergy. So many misconceptions, misunderstandings, fears and confusion locked up behind those few words for both moms and health-care professionals. I was privileged to attend the congress of the European Academy of Pediatrics two weeks ago and the master course focused on nutrition in childhood. I finally have a better understanding of CMPA (Cow’s Milk Protein Allergy) and I hope I can explain it better to you too.

As with many food allergies, CMPA is an allergy (where the immune system mistakenly identifies a protein as harmful and reacts to cause symptoms) to one or multiple of the different protein-structures in cow’s milk. Unfortunately the occurrence of all types of allergies are increasing in Western societies at an alarming rate, with CMPA being the most common (2-7% of babies). Food allergies specifically can cause a lot of anxiety in parents and children as you have to be on alert at all times, and any symptom can be seen as an allergic response. It is high maintenance to totally exclude a specific food group from your child’s diet and this can also cause deficiencies in their diet. It is thus important that your child is diagnosed correctly, and that you have the necessary dietary assistance to help you and your child reach the top of this mountain.

The good news about CMPA specifically is that many babies outgrow it by 1 year of age, and most children should tolerate cow’s milk proteins by the age of 3 years and can return to a normal diet. Having a sibling with CMPA does not increase a new baby’s chance to develop CMPA, but if there is a family history of atopy/allergies the 2nd child will have the same type of risks as the first.

It is important to know that not all symptoms caused by ingesting food are caused by an allergy.

Dr Nické Theron

Lactose intolerance is one example, where poor breakdown (by an enzyme called lactase) and absorption of the sugar component (lactose) in cow’s milk, causes too much lactose to end up in the large intestines resulting in symptoms such as bloating, diarrhoea and abdominal pain. This is very rare in infants who usually have enough lactase-enzymes to digest the lactose in up to 1 litre of breast milk per day. Any left-over lactose in an infant’s gut acts as a prebiotic and improves the development of the immune system. As a baby starts to wean, the lactase percentage drops slowly in about 70% of the population, and this could lead to symptoms of lactose intolerance after the age of 5 years. Even in these children it is usually not necessary to cut out all lactose from their diets as they can cope with a small amount. Premature babies might have lactose intolerance due to their immature gut, and very rarely babies are born with a congenital abnormality where they produce no lactase and they will then present with severe diarrhoea.

Another more common cause of lactose intolerance is a sick gut (secondary lactose intolerance). If your baby had a bout of infective diarrhoea or has severe inflammation of the gut due to eg CMPA, the inside lining of the intestines becomes very thin and then lactase cannot be produced. Removing lactose from the diet can then help to give the intestines a chance to restore the lining and lactose can be reintroduced after 2-4 weeks.

Ok, back to CMPA:
This allergy can develop in exclusively breastfed babies as the cow’s milk protein is passed relatively unchanged through the breastmilk. It can also present later when cow’s milk is introduced into a baby’s diet.


Unfortunately there is not one specific symptom for CMPA, and babies and children can present with a wide variety of symptoms. It can cause anything from vomiting, regurgitation (can be misdiagnosed as reflux), blood in the stools, diarrhoea, constipation, eczema, wheezing or anaphylaxis (a state of shock where the allergic reaction overwhelms the body and is a medical emergency). See the table below for more detail.

Some babies become critically ill shortly after ingesting the protein, while others are happy, healthy and growing with some nagging symptoms. I am sure you can now understand why it is so difficult to diagnose CMPA!

To complicate the matter and the diagnosis even more, there are different types of CMPA because of the different ways the immune system responds to the protein. Some children will have “IgE-mediated CMPA”. (IgE is a specific antibody of the immune system that recognizes proteins as bad and rapidly responds to it.) Children with asthma and eczema also have high levels of IgE in their blood. The advantage is that we can test for this type. They will usually have a positive skin-prick test and positive blood results specifically for CMPA. The disadvantage of this type is that the children usually take longer to outgrow the allergy, and they are more prone to develop other atopic diseases later in life. Their reaction to CMP is also usually more severe and they can develop anaphylaxis.

The immune system can also respond without IgE, leading to a more delayed reaction (some children can still get very ill!) that is usually outgrown earlier. However there are no tests we can do to prove this type of allergy and this can be very frustrating to parents and doctors!

The latest guidelines have thus suggested that the best way to diagnose any type of CMPA is with a good history and physical examination, followed by an elimination of the cow’s milk protein from the diet. If the symptoms improve the child should be “challenged” by giving the cow’s milk protein again, and if the symptoms return the diagnosis is confirmed.

Other tests that might be done are blood tests for total IgE and specific food allergies or a skin-prick test where the reaction of the skin to different allergens are tested.

I will leave you so that you can digest this chunky piece of information, please feel free to ask if you do not understand anything! In my next post I will address the management of Cow’s Milk Protein Allergy from a medical perspective and help you to understand where a Dietitian fits into the picture.


  1. Ralf G. Heine, Fawaz AlRefaee, Prashant Bachina, Julie C. De Leon, Lanlan Geng, Sitang Gong, José Armando Madrazo, Jarungchit Ngamphaiboon, Christina Ong, and Jossie M. Rogacion; “Lactose intolerance and gastrointestinal cow’s milk allergy in infants and children – common misconceptions revisited”; World Allergy Organ J. 2017; 10(1): 41.
  2. Yvan Vandenplas, Martin Brueton, Christophe Dupont, David Hill, Erika Isolauri, Sibylle Koletzko, Arnold P Oranje, and Annamaria Staiano; “Guidelines for the diagnosis and management of cow’s milk protein allergy in infants”; Arch Dis Child. 2007 Oct; 92(10): 902–908.
  3. Koletzko S, Niggemann B, Arato A, Dias JA, Heuschkel R, Husby S, Mearin ML, Papadopoulou A, Ruemmele FM, Staiano A, Schappi MG, and Vandenplas Y; “Diagnostic Approach and Management of Cow’s-Milk Protein Allergy in Infants and Children: ESPGHAN GI Committee Practical Guidelines”

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