Cow’s Milk Protein Allergy (CMPA): Symptoms, Diagnosis & Treatment
If your baby is unsettled, rashy, gassy, or reacting after feeds, it’s normal to wonder whether cow’s milk could be part of the problem. Many parents describe the same worries: green or mucusy stools, reflux that doesn’t settle, red eyelids, or eczema flares, and often feel confused or dismissed. Cow’s milk protein allergy affects around 2% of infants in Australia (about 1 in 50), so you’re not imagining it, and you don’t have to work it out alone.
This guide brings together current evidence and the clinical experience of our GPs to help you recognise symptoms, understand diagnosis, and know when to seek support.
What Is Cow’s Milk Protein Allergy?
Cow’s milk protein allergy (CMPA) occurs when a baby’s immune system reacts to proteins in cow’s milk, usually casein and whey. This reaction can cause inflammation in the gut, skin, or airways. CMPA can affect babies who are breastfed, formula-fed, or mixed-fed.
CMPA is often confused with lactose intolerance, as there are some similar symptoms. Here’s a simple way to understand the difference:
CMPA is an immune reaction causing rashes, vomiting, blood in stools, wheeze, or swelling.
Lactose intolerance is a digestive issue and causes wind, bloating, or diarrhoea only. It is very rare in young babies.
Types of Cow’s Milk Protein Allergy
Not every baby reacts the same way:
1. Immediate reactions After Milk (IgE-mediated)
Symptoms appear within minutes to two hours.
2. Delayed reactions (non-IgE-mediated)
Symptoms develop hours or days later.
3. Mixed reactions
Some babies experience both fast and delayed symptoms. This means they may develop hives or swelling soon after feeding, but also have ongoing gut symptoms or eczema that worsen over time.
What Symptoms Should I Look For if My Baby Might Have CMPA?
Digestive symptoms (Very Common)
These symptoms can appear quickly or build up slowly over days:
Vomiting or frequent reflux
Diarrhoea, loose stools
Mucus or blood in stools
Tummy cramps, wind, or colic-like crying
Poor feeding or refusal to feed
A GP can help separate normal infant reflux from symptoms more likely caused by milk protein allergy.
Skin symptoms
Common skin symptoms include:
Eczema that keeps flaring (most common symptom in breastfed babies with CMPA)
Hives or raised rashes
Red or itchy patches
Swelling around the lips, eyes, or face (usually immediate)
Respiratory symptoms (Usually in Faster Reactions)
These symptoms may be mild or part of a more serious reaction:
Sudden wheezing
Persistent cough
Runny nose or sneezing shortly after milk
If your baby shows breathing symptoms soon after milk, seek urgent medical advice.
Severe allergic reactions (anaphylaxis)
These reactions are rare but serious. Signs include difficulty breathing, swelling of the tongue or throat, sudden floppiness, or hoarse crying.
➡️ If you suspect anaphylaxis, act immediately:
Use your child’s EpiPen (or Anapen) first if they have one, even if you’re not completely sure.
Call Triple Zero (000) straight after using it.
Lay your baby flat or hold them in your arms.
Do not let them stand or walk.
A second dose can be given after 5 minutes if symptoms are not improving.
This early treatment keeps your child safe while help is on the way.
How CMPA Is Diagnosed
There is no single test for all types of CMPA. Diagnosis usually involves:
1. Reviewing Your Baby’s Symptoms and History
Your GP will look at:
When symptoms appear
Whether they improve when milk is reduced
Any eczema, reflux, or family history of allergies
A symptom diary is incredibly helpful for your doctor to work out whether milk is the likely trigger. It doesn’t need to be perfect. Just note:
What your baby ate
When symptoms appeared
How long they lasted
Anything that made them better or worse
2. Allergy Tests (When They’re Helpful and When They Aren’t)
Allergy tests can be useful if your baby has quick reactions to milk. In these cases, your GP or paediatrician may suggest:
Skin prick tests, which check for fast reactions to milk proteins
Blood tests (specific IgE), which measure the same type of response
If your baby has delayed symptoms, the tests often come back negative. This is normal and means your baby’s reaction uses a different part of the immune system.
3. Elimination Diet and Food Challenge (The Gold Standard for Diagnosis)
A short, supervised trial without cow’s milk followed by a planned reintroduction is the most reliable way to confirm CMPA. Your GP will guide each stage.
Treating and Managing CMPA
The goal is simple: reducing symptoms while keeping your baby well-nourished.
1. Avoiding Milk Safely (Elimination Diets)
The first step in managing CMPA is usually removing all cow’s milk protein from your baby’s diet.
If you are breastfeeding: you may need to remove dairy from your own diet for a short period.
Important: Avoid removing dairy without medical advice. Babies grow fast, and removing milk too broadly can affect nutrition if not supervised.
2. Formula Options for Babies With CMPA
Parents often try goat’s milk or ‘sensitive’ formulas first, but these still contain milk proteins and usually don’t help CMPA. When switching to a CMPA-appropriate formula, some babies take a few days to adjust. Poos may take a couple of weeks to settle, which is normal.
Your GP may suggest one of the following:
Extensively Hydrolysed Formula (EHF)
First-line choice for most babies with CMPA
Less likely to trigger an immune reaction
Not suitable if your baby has had anaphylaxis to cow’s milk
Amino Acid Formula (AAF)
Used for babies who cannot tolerate EHF
Suitable for severe allergies and multiple food allergies
Soy formula
Sometimes suitable for babies over 6 months if soy allergy is not present.
3. Breastfeeding and CMPA (Maternal Elimination Diets)
You can continue breastfeeding. Breast milk supports your baby’s gut and may help them build tolerance over time. Removing dairy from your diet often improves symptoms within 72–96 hours. A dietitian may recommend calcium, iodine, B12 or vitamin D supplements if you need to stay dairy-free for longer.
4. Making Sure Your Baby Gets Enough Nutrition
Your GP will monitor your baby’s weight and feeding to ensure they continue to grow well. Of note, plant-based milks (almond, oat, rice) are not suitable as a main drink for babies under 12 months.
When to See a Doctor
Book a GP appointment if your baby has:
Blood or mucus in stools
Poor weight gain
Ongoing reflux
Eczema that keeps flaring
Vomiting after most feeds
Frequent loose stools
Wheeze or cough after drinking milk
Severe fussiness or back-arching during feeds
If symptoms appear suddenly, such as swelling, breathing changes, or a child becoming pale or floppy, follow emergency instructions immediately.
Book a Consultation at Mona Vale Doctors
If you’re worried, a GP at Mona Vale Doctors can support you with:
Clear assessment of your baby’s symptoms
Safe guidance on elimination diets
Advice on breastfeeding or formula options
Monitoring your baby’s growth
Planning the right time to reintroduce dairy
Coordinating specialist care if needed
Book online or call our practice to make an appointment.
We’ll walk with you through each step so you feel confident, supported and informed.
FAQs
What are the most common symptoms of cow’s milk protein allergy in babies?
Digestive symptoms are very common: vomiting, reflux, diarrhoea or mucus in stools. Skin reactions such as eczema flares or hives can also appear. Some babies develop respiratory symptoms like wheezing or coughing soon after feeds.Can CMPA cause skin rashes or eczema in infants?
Yes, CMPA can lead to eczema that keeps flaring or worsening. Fast reactions may also cause hives or swelling shortly after milk.Will my child grow out of cow’s milk protein allergy?
Most children outgrow CMPA. In Australia, around 80% tolerate cow’s milk by ages 3–5. Delayed (non-IgE) reactions often resolve earlier, while immediate (IgE) allergies may take longer. But every child is different: a small number may continue to react beyond early childhood. It only means their allergy simply follows a different timeline.
References
Australasian Society of Clinical Immunology and Allergy. (2024). Cow’s milk (dairy) allergy. ASCIA. https://www.allergy.org.au/patients/food-allergy/cows-milk-dairy-allergy. Last consulted 18 November 2025.
Caffarelli, C., Giannetti, A., Buono, E. V., Cunico, D., Carbone, R., Tonello, F., & Ricci, G. (2025). Cow’s Milk Allergy in Breastfed Infants: What We Need to Know About Mechanisms, Management, and Maternal Role. Nutrients, 17(11), 1787. https://doi.org/10.3390/nu17111787
D'Auria, E., Salvatore, S., Acunzo, M., Peroni, D., Pendezza, E., Di Profio, E., Fiore, G., Zuccotti, G. V., & Verduci, E. (2021). Hydrolysed Formulas in the Management of Cow's Milk Allergy: New Insights, Pitfalls and Tips. Nutrients, 13(8), 2762. https://doi.org/10.3390/nu13082762
Darma, A., Sumitro, K. R., Jo, J., & Sitorus, N. (2024). Lactose Intolerance versus Cow's Milk Allergy in Infants: A Clinical Dilemma. Nutrients, 16(3), 414. https://doi.org/10.3390/nu16030414
Høst, A., Husby, S., & Osterballe, O. (1988). A prospective study of cow's milk allergy in exclusively breast-fed infants. Incidence, pathogenetic role of early inadvertent exposure to cow's milk formula, and characterization of bovine milk protein in human milk. Acta paediatrica Scandinavica, 77(5), 663–670. https://doi.org/10.1111/j.1651-2227.1988.tb10727.x
Escobar-Sáez, D., Montero-Jiménez, L., García-Herrera, P., & Sánchez-Mata, M. (2022). Plant-based drinks for vegetarian or vegan toddlers: Nutritional evaluation of commercial products, and review of health benefits and potential concerns.. Food research international, 160, 111646 . https://doi.org/10.1016/j.foodres.2022.111646.
