Signs of Cow’s Milk Protein Allergy (CMPA) in Breastfed Babies
What Parents Should Know
Many breastfeeding mums worry when their baby is unsettled, has tummy issues, or has skin problems that don’t seem to improve. It can be confusing to work out what is normal and what might be a sign of Cow’s Milk Protein Allergy (CMPA).
CMPA is one of the most common food allergies in babies, but it can be hard to spot, especially in breastfed babies. If you feel something isn’t quite right, you are not alone. With the right support, most babies improve quickly.
As a paediatric allergy dietitian, I help mums every day to understand these symptoms and guide them through the safest way to diagnose and manage CMPA.
What Is CMPA
CMPA happens when a baby’s immune system reacts to the protein in cow’s milk. For breastfed babies, small amounts of cow’s milk protein can pass through your breastmilk and cause symptoms. For formula fed babies, it may be more obvious when cows milk formula is introduced.
There are two types
IgE-mediated, where symptoms happen fast
Non-IgE mediated, where symptoms are delayed and can take hours or days to appear
Breastfed babies most commonly have the delayed type, which is why it can be difficult to recognise.
Signs of CMPA in Breastfed Babies
Your baby does not need all these symptoms. Some babies only have one or two.
Tummy and Stool Symptoms
This is one of the most common areas where parents notice changes.
You might see:
mucus in the poo
Small streaks of blood
Loose, frothy, or very frequent stools
Reflux that doesn’t improve
Vomiting
Bloating, gas or tummy pain
Pulling off the breast because feeding hurts their tummy
Skin Symptoms
Some babies show signs on their skin.
Eczema that doesn’t settle
Redness around the mouth
Hives or swelling (more common in fast reactions)
Behaviour and Feeding Changes
Babies show discomfort through their behaviour.
Crying more than usual
Very unsettled
Poor sleep
Back arching during or after feeds
Wanting to feed very often but seeming uncomfortable
Or feeding less because it hurts their tummy
Many mums describe it as “something just feels off.”
Why CMPA Can Be Hard to Identify in Breastfed Babies
Breastfed babies often have delayed symptoms
There is no single test that can diagnose non-IgE CMPA
Symptoms can look similar to reflux, colic or normal newborn behaviour
Many mums worry they are doing something wrong when they’re not
This is why getting support from the right health professional makes such a big difference.
Who Should You See
For babies, the best health professional to support CMPA diagnosis and management is a paediatric allergy dietitian.
Your medical team (GP, Paediatrician) can help diagnose CMPA and/or rule out medical concerns.
A paediatric allergy dietitian can then:
Helps you understand your baby’s symptoms
Guides safe dairy elimination in your own diet
Makes sure your diet stays balanced
Assesses whether symptoms match CMPA
Develops a clear plan to test if milk is the cause
Supports you through reintroduction later on
Helps you start solids safely
CMPA diagnosis should never be done by guesswork. Removing dairy “just to try it” without guidance can lead to confusion, stress and an unclear diagnosis.
How CMPA Is Diagnosed
There is no blood test or skin test for the delayed (non-IgE) type of CMPA.
Diagnosis is done by
Removing dairy from your diet with professional support
Watching for improvement over 2–4 weeks
Reintroducing dairy in a planned and supervised way to confirm the diagnosis
This step is important. Without reintroduction, we cannot know for sure if dairy was the cause.
A paediatric allergy dietitian helps make sure this process is safe and clear.
How CMPA Is Managed
If you are breastfeeding, you may need to remove dairy from your diet for a short time. You will get support to ensure you still meet your nutritional needs, especially calcium.
Most babies improve within 1–2 weeks once the right changes are made.
Later on, milk is reintroduced at the correct time using a step-by-step approach such as a milk ladder. This helps us check if your baby has outgrown the allergy. If there are signs of an ‘fast type’ reaction eg IgE mediated food allergy, you will require support from a Paediatric Allergist as well.
Do Babies Grow Out of CMPA
Yes. Most babies grow out of CMPA.
Many by one year of age
Most by two to three years
A dietitian guides this process to make sure it is done safely.
Final Thoughts for Breastfeeding Mums
If your baby seems unsettled, has ongoing tummy symptoms, or you just feel that something isn’t right, trust your instincts. CMPA can be tricky to understand on your own, and you shouldn’t have to figure it out without help.
A paediatric allergy dietitian is the best person to guide you through diagnosis, support you while breastfeeding, and make a clear plan so you can feel confident again.
You don’t have to guess or struggle alone. With an experienced paediatric allergy dietitian, you will feel supported every step of the way.
