Cow’s milk protein allergy (CMPA) is the most common food allergy affecting children all over the world.

The symptoms can be delayed (non-IgE mediated) or immediate (IgE mediated) or a mixture of the two. CMPA may affect a baby who is formula fed, combi fed and a breastfed baby can also be affected since dairy can pass through mother’s milk into the baby.

What causes CMPA?

The risk of developing CMPA increases if there is a family history of eczema, hay fever and food allergies. Environmental factors that may affect a baby’s gut health have also been shown to contribute.

These include antibiotic use, the use of protein pump inhibitors such as omeprazole and being born via C-section.  Some research suggests that low blood vitamin D level is a risk factor for food allergy. Vitamin D deficiency predisposes to gastrointestinal infections, which may promote the development of food allergies.

What are the symptoms of CMPA?

There is a very large range of symptoms that may present in a child with CMPA.

In some children, multiple symptoms can coexist whereas, in others, it may only be one symptom. For example, some children “only” have constipation whereas some may have colic, loose stools, eczema, and reflux. Allergy may be IgE mediated with rapid onset of symptoms or non-IgE mediated, producing more delayed symptoms.

Some have a mixture of the two. Please see below for more information about the symptoms of CMPA.

Table 1: Symptoms of IgE and non-IgE mediated CMPA

Non-IgE mediated


  • Gastro-oesophageal reflux disease
  • Loose stools
  • Blood and/or mucus in the stools
  • Abdominal pain
  • Infantile colic
  • Food refusal
  • Constipation
  • Perianal redness
  • Faltering growth plus one or more gastrointestinal symptoms above (with or without significant atopic eczema)


  • Mucus in the back of the nose, sinus or throat


  • Itchy skin
  • Skin rash
  • Atopic eczema

IgE mediated


  • Swelling of the lips, tongue, and palate
  • Itchy mouth
  • Nausea
  • Colicky abdominal pain
  • Vomiting
  • Diarrhoea


  • Nasal itching, sneezing or congestion.
  • Cough, chest tightness or wheezing


  • Itchy skin
  • Skin rash
  • Acute rash
  • Acute swelling (most commonly in the lips and face, and around the eyes)

Other symptoms seen in clinical practice but may not be evidence based:

  • Recurrent ear infections
  • Poor sleep

CMPA is NOT lactose intolerance

True lactose intolerance is due to a deficiency of the enzyme lactase; it is not an allergy. Primary lactase deficiency is genetic and doesn’t usually present until later childhood or adult life and is due to a reduced ability to produce the enzyme lactase.

In children, we are most likely to see what is known as secondary lactose intolerance which is caused by an injury to the small intestine, from acute gastroenteritis or diarrhoea.

Therefore, if your child has struggled with loose stools, they have secondary lactose intolerance which usually subsides after a period of 4-6 weeks on a lactose-free diet.

How do we diagnose CMPA?

Your dietitian or doctor will perform an allergy focused assessment to help exclude or diagnose CMPA. There are no validated tests to diagnose non-IgE-mediated CMPA, therefore diagnosis is based on a combination of an allergy-focused history and an elimination diet where the allergen is eliminated from the diet for a period of time.

The allergen is then reintroduced back into the diet and if a reaction occurs, an allergy is confirmed. A skin prick test or blood test to check for circulating IgE antibodies is indicated in children with suspected mediated CMPA.


For example, a mother is breastfeeding her infant and has noticed her baby is unsettled, struggling with colic and reflux. She speaks to her dietitian and is advised to go dairy-free for 2-4 weeks. Mom sees a marked improvement in her baby’s symptoms. To confirm an allergy, mom has a glass of cow’s milk or cheesy pizza and notices the symptoms reappearing which confirms non-Ige CMPA.

A formula-fed infant is struggling with loose stools, arching their back in pain and congestion. Mom tries an extensively hydrolysed formula (available by contacting your dietitian or doctor) and notices a marked improvement in her baby’s symptoms. After 2-4 weeks, ordinary cow’s milk formula is introduced again, step by step. See table below. If symptoms reappear, the child has a confirmed allergy to cow’s milk.

At times, the diagnosis is pretty clear, and your dietitian or doctor may therefore omit this step.

Table 2: Home reintroduction to Confirm or Exclude CMPA

Day Volume of boiled water (mls) Hypoallergenic formula (mls) Cow’s milk formula (mls)
Day 1 210mls 180mls 30mls
Day 2 210mls 150mls 60mls

Will my child outgrow their allergy?

The good news is that it is more likely for a child with an allergy to milk or even egg to outgrow their allergy than children with an allergy to peanuts.

For example, only 10% outgrow their allergy to peanut whereas in children with an allergy to dairy, the majority (85%) would have outgrown their allergy by age 3. The likelihood to outgrow a food allergy, therefore, depends on the Food BUT also the Severity of the allergy.



Luyt, D.Ball, H.Makwana, N.Green, M. R.Bravin, K.Nasser, S. M.Clark, A. T.Clinical & Experimental Allergy2014 ( 44642– 672.iMAP Home Reintroduction to Confirm or Exclude the Diagnosis of Mild-toModerate Non-IgE Cow’s Milk Allergy

Mitre E, Susi A, Kropp LE, Schwartz DJ, Gorman GH, Nylund CM. Association Between Use of Acid-Suppressive Medications and Antibiotics During Infancy and Allergic Diseases in Early Childhood. JAMA Pediatr. 2018;172(6):e180315. doi:10.1001/jamapediatrics.2018.0315

NICE guidelines (2015) “Cow’s milk protein allergy”

Walsh J, Meyer R, Shah N, Quekett J, Fox AT. Differentiating milk allergy (IgE and non-IgE mediated) from lactose intolerance: understanding the underlying mechanisms and presentations. Br J Gen Pract. 2016;66(649):e609-e611. doi:10.3399/bjgp16X686521