Written by Registered Dietitian Nishti

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 the 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?

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.


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.

Real Case Examples:

For example, a mother is breastfeeding her infant and has noticed her baby is unsettled, and 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 the 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

DayVolume of boiled water (mls)Hypoallergenic formula (mls)Cow’s milk formula (mls)
Day1 210mls180mls30mls
Day2 210mls150mls60mls

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 peanuts 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.

If this blog post was helpful, please leave a comment below and share it with a parent who you may think could benefit from reading this. Thanks for reading to the end. If you are interested in more videos on cow’s milk protein allergy please visit Nishti’s Choice on Youtube.

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1 Luyt, D., Ball, H., Makwana, N., Green, M. R., Bravin, K., Nasser, S. M., Clark, A. T.. Clinical & Experimental Allergy, 2014 ( 44) 642– 672.iMAP Home Reintroduction to Confirm or Exclude the Diagnosis of Mild-toModerate Non-IgE Cow’s Milk Allergy

2 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

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

4 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