CMPA Symptoms

What is CMPA?

CMPA or cow’s milk protein allergy is one of the most common allergies in children, estimated to affect around 2-3% of babies before 6 months old. 

It is caused by the immune system responding to the protein found in cow’s milk. There are many different symptoms of CMPA and how severe the symptoms are can differ between babies.

It can also be very confusing to know whether the symptoms that your baby shows are due to a cows milk protein allergy or just typical of a baby their age. 

In this blog, I will discuss the symptoms of CMPA.

How do I know if my baby has CMPA?

There are many different symptoms including;

  • Gastrointestinal (tummy) – stool changes – mucous and/or blood in stool/constipation/loose stools
  • Respiratory – snuffly baby/changes in breathing/congestion
  • Skin – rash/reddening/itchy

However, the symptoms can vary from baby to baby and from mild to moderate to severe.

It is important that when you speak with a health professional that they discuss the severity of the symptoms and the speed which they happen. This can support diagnosis of IgE or non IgE milk allergy – Read on to find out more.

Symptoms of CMPA
CMPA Symptoms

What triggers CMPA?

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

When a baby with milk allergy is given formula milk containing cow’s milk protein, or breastfeeding and mum has milk in her diet, 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.  

At what age does it start?

CMPA symptoms usually can start within the first few weeks after birth, but can be a little delayed and could start anytime up to 2-3 months old.

IgE vs non IgE mediated allergy.

There are two different types of CMPA

They are IgE (immunoglobulin E) mediated, and non IgE (non immunoglobulin) mediated.

Immunoglobulins are another word for antibodies.

Mediated means to cause.

So an IgE reaction involves antibody production, and in non-IgE reactions there is no antibody involvement. However both IgE and non IgE are food allergies, not an intolerance (I hear other health professionals saying this so often and it really gets my back up!)

It is generally the symptoms of non IgE milk allergy that are misdiagnosed as lactose intolerance.

Milk Allergy vs Lactose Intolerance

Just to note; lactose intolerance is the bodies reaction to the sugar lactose in the milk and generally causes tummy trouble (no skin reaction or changes to airways). Lactose intolerance is also very rare in babies.

CMPA is an allergic reaction to the protein in cows milk.

These are two completely different diagnoses.

What are the symptoms of CMPA in babies?

The table shows the different symptoms of CMPA.

The main difference you can see, and that I talk to parents a lot about is that symptoms in an IgE reaction are immediate and in a non-IgE reaction symptoms are delayed. You will also find that in IgE CMPA that swelling is a symptom, whereas in non-IgE milk allergy swelling does not occur.

IgE vs Non IgE Milk Allergy Symptoms

IgE Milk Allergy SymptomsNon IgE Milk Allergy Symptoms
An immediate reaction within minutes and up to 2 hours after having milk protein. A delayed reaction which happens between 2-72 hours after having milk protein.
Swelling to lips, face or eyes/
Skin reaction – hives, raised, itchy rash (urticaria), reddening. Skin reaction – Itchy skin, reddening ‘erythema’, atopic eczema.  
Gastrointestinal upset – nausea, vomiting, diarrhoea, tummy pain or discomfort,  Gastrointestinal upset – Reflux, vomiting, diarrhoea, blood and/or mucous in stools, constipation, tummy pain or discomfort, irritability. 
Respiratory – cough, chest tightness, wheezing and shortness of breath. Nasal itching, sneezing, congestion, conjunctivitis. Respiratory – Cough, chest tightness, wheezing and shortness of breath. 
CMPA Symptoms

NICE 2021 (3) 


Skin reactions are present in both IgE and non-IgE milk allergies so it is important that you check how soon the symptoms start and whether the rash is raised.


In both IgE and non IgE CMPA baby’s there may be changes in stools (poop). Symptoms can range from constipation to very loose stools (some babies can poo up to 20 times per day). Stools may also have mucous or blood present.

Remember, constipation does not typically happen in a baby with an IgE allergy.

CMPA Respiratory

Coughing is a symptom of both IgE and non-IgE milk allergy. But if your baby is congested, is always sneezing, or has repeated conjunctivitis then it may be that they have an IgE milk allergy.

In more severe cases of IgE CMPA allergic symptoms such as breathing difficulty can occur; also known commonly as anaphylaxis. Anaphylaxis is a narrowing of the airways and can be life threatening. If you find your baby showing swelling and breathing difficulty then go immediately to your nearest emergency department.

The confusion with diagnosis of milk allergy

As you can see there are many different symptoms of CMPA, but it is important that the correct diagnosis is made as misdiagnosis is very common. That’s where an expert milk allergy dietitian like me comes in.

To diagnose your baby with a milk allergy they should show one of more of the symptoms in the table above. The guidelines also say that these symptoms should not have been reduced by other support.

Examples of when it may not be CMPA

  • Reflux – if your baby has reflux and you have been advised on techniques to help or prescribed medication and this has relieved reflux then it is unlikely that this is due to milk allergy.
  • Constipation – if your baby is constipated and you have tried tummy massage, warm baths and/or medication and this helped to relive constipation then again it is unlikely that this is due to milk allergy.

If you have tried all the remedies and symptoms are still continuing then YES it may be that your baby has CMPA.

But…it’s not just about the symptoms of milk allergy that lead to the diagnosis

It is also important that the clinician you talk to takes a full allergy-focused history to ensure again the correct diagnosis for your baby.


I hope this helps to support the signs and symptoms of cows milk protein allergy. If you are concerned that your baby has a milk allergy then get in touch and I can help you out with the correct diagnosis. Remember that a non-IgE allergy cannot be diagnosed with a blood or RAST test. This is only for an IgE allergy.

You can use my milk allergy symptom checker to help to log your symptoms, find it here

Hannah x

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