CMPA Breastfeeding 

By Hannah Whittaker RD, PGDip | Dec 21, 2022

The milk challenge

Milk allergy is one of the most common food allergies affecting between 2-3% of babies under 6 months. To diagnose milk allergy in a breastfed baby mums need to complete a milk challenge. This can be confusing and you might have many questions about how to start.

You wonder, should you have a little bit of cheese or yogurt? or should you be having a full glass of milk each day? How much is it?

Read on to find out my evidence based advice on how I would support diagnosis of CMPA in breastfed babies and how best to complete the milk challenge to confirm this diagnosis. 


What triggers CMPA?

CMPA (cows milk protein allergy) is a condition that is caused by the body reacting to the proteins found in cows’ milk.

When a baby has milk allergy and their mum eats or drinks products containing cow’s milk protein, the baby’s body goes into a defense mode. Their body is defending against the milk protein as if it is an invader, this causes an allergic reaction and the symptoms to occur.  

Can breastfed babies have CMPA?

The short answer is yes. However, the evidence shows us that breastfed babies are less likely to have CMPA over formula-fed babies. One study showed that 0.5% of breastfed babies had CMPA vs 2-7.5% of formula-fed babies.

This is thought to be due to the differences in the gut bacteria of breastfed babies. It is also thought that the level of cows milk protein in breastmilk is 100,000 times lower than in formula milk.

How does the milk protein I eat get to my baby?

When you eat foods containing milk protein some of this may travel through your breastmilk to your baby, much like most other nutrients you eat.

How much milk protein is in my breastmilk?

The answer is we’re just not sure and with all nutrients this can differ between mum.

Diagnosis of CMPA

Diagnosis can be difficult whether breast of formula feeding, but when breastfeeding it can make it a little more difficult. You’re just not sure how much milk protein is getting to your baby from what you eat and drink.

The diagnosis can also depend on who you seek help from first. Health professional’s knowledge can vary greatly and some may just not seem confident in the advice they are giving.

The main tricky part is that symptoms of non IgE milk allergy can be similar to those symptoms in a newborn baby. I’m talking changes in poop and general tummy upset.

This means that underdiagnosis and overdiagnosis of milk allergy is common

You can find more information on the symptoms of CMPA here;

How long does dairy stay in breastmilk?

A small study in 2019 has shown that milk protein may leave mum’s milk after as little as 6 hours. Wow, that’s quite quick right!

This study recruited breastfeeding mums who were following a milk protein-free diet and gave them milk to drink. They found that in the samples of breastmilk taken, after 2 hours milk protein levels peaked, and by 6 hours were no longer present.

More research is needed in this area, however the small study showed results which supports our current guidance.

CMPA Breastfeeding – The Milk Challenge

A dairy-free diet when breastfeeding

So, a full allergy focused history has been taken and your baby is showing symptoms of CMPA that haven’t responded to treatment. To give you an example; if it is suspected your baby has reflux then first a feeding assessment should be completed checking for tongue tie and observing latch. This is to make sure that the cause of reflux or tummy pain isn’t due to your baby taking in excessive air when feeding.

So other causes of symptoms have been ruled out. It is suspected that your baby has delayed CMPA (non IgE) and you have been advised to follow a dairy free breastfeeding diet.

The guidelines advise following a dairy free breastfeeding diet for 2-4 weeks.

Remember that if symptoms don’t settle for your baby after this time then it is unlikely that they were due to cows milk protein and further investigation is needed. 

What is the milk challenge?

This is how we diagnose non IgE (delayed) cows milk protein allergy. It is not to be used if your baby has an IgE or immediate milk allergy. See symptoms of milk allergy for more info on this. 

So the common questions you need the answers to when it comes to CMPA breastfeeding and the milk challenge.

My baby is unwell, can i do the milk challenge?

The list below is the circumstances when you shouldn’t start the milk challenge with a breastfed baby.

  • If your baby is unwell – tummy bug, high temperature, heavy cold
  • If they are teething which is causing discomfort – upset stomach, red cheeks, not sleeping – general teething is fine.
  • If they are taking prescribed medication which may cause tummy upset.
  • If they are having a flare up of eczema
  • If they have suspected symptoms of an IgE (immediate) allergy to milk protein

How do I complete the milk challenge when breastfeeding?

So you have followed a dairy free breastfeeding diet for 2-4 weeks and symptoms have settled for your baby.

The next steps are the reintroduction – you can find my CMPA breastfeeding milk challenge tracker here to help

What you need to now start doing is to put cows milk protein contained products back into your diet.

It is up to you whether you go back to the milk protein you were having in your diet before the 2-4 weeks of elimination. Or, you can do this slowly. I would though advise you to monitor symptoms at each stage.

Monitoring symptoms means that if your baby does have a reaction then you know when and how much milk protein they were able to tolerate through your breastmilk. 

What if my baby has a reaction to my breastmilk?

If you start to reintroduce milk back into your diet and your baby starts again with their original symptoms then stop the challenge and go back to a strict dairy free breastfeeding diet. You will then definitely need a dietitian to support you to ensure nutritional balance for both you and your baby. Remember you will be avoiding the main calcium-rich products and your calcium requirements increase to 1250mg when breastfeeding.

What if my baby doesn’t have a reaction to the milk challenge?

Then it is likely that they don’t have a milk allergy and this was misdiagnosed. It may have been a little tummy bug after birth, reflux or colic that caused symptoms. You can then freely reintroduce milk protein back into your diet. 

Remember – as milk protein in breastmilk is thought to be 100,000 lower than in formula milk. This means that in a breastfed baby that symptoms could start when weaning and your baby is having cows milk contained products. Especially if your diet is low in milk protein and there is a family history of allergy.

If you’re worried get in touch.


So, yes breastfed babies can have a milk allergy but it is important that the correct diagnosis is made if CMPA is suspected. This is done by the milk challenge in non IgE (delayed) milk allergy.

And finally, don’t let anyone tell you have to stop breastfeeding if your baby has a milk allergy – this is not true and really infuriates me! With correct support in nutritional balance you and your baby will get all the nutrients you need when following a strict milk free diet. Contact me if you need support

Here’s the link to my free CMPA Breastfeeding tracker & guide too.

CMPA Breastfeeding

Hannah x

Hannah Whittaker Dietitian Bump2baby Nutrition
Expert Pregnancy & Paediatric Dietitian at | | Website | + posts

Hannah is an Expert Registered Dietitian specialising in Vegan Family Nutrition and Cows Milk Protein Allergy. 

She is a respected figure in the field of nutrition and a captivating speaker and sought after media spokesperson being featured in esteemed publications including the Sunday Times, Independent and Huffington Post.


  • Registered Dietitian
  • First Class Degree in Nutrition


  • Over 15 years experience working in the field of nutrition
  • Respected Media Spokesperson both in the UK & USA; quoted online, TV and in local and international news
  • Writer & Researcher, supporting the BDA and PEN Nutrition



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