CMPA and Breastfeeding; Let’s talk milk protein allergy

Navigating the world of food allergies can be daunting, especially when it comes to CMPA (cow’s milk protein allergy) and breastfeeding. 

CMPA or milk allergy commonly affects 2-3% of babies under six months old. 

If you are breastfeeding and suspect that your baby’s symptoms may be due to milk allergy you probably want to know how you would get a clear diagnosis. There are two different ways that a milk allergy diagnosis can be made and the information in this blog will guide you correctly through this process. 

But first I want to make sure you have all the information to understand what triggers CMPA, the likelihood of your breastfed baby experiencing a food allergy, and how we would manage and confirm this diagnosis effectively.

What triggers CMPA?

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

When a mum who is breastfeeding consumes products containing cow’s milk protein, it can affect her baby if they have a cow’s milk protein allergy (CMPA). 

Cow’s milk protein, made up of amino acids, needs to be broken down by the body to be used. However, in milk allergy the baby’s immune system mistakenly identifies this protein as harmful. This triggers a defense response, leading to an allergic reaction.

How common is CMPA in breastfed babies?

Yes, breastfed babies can have a milk allergy, but it is less common compared to formula-fed babies. Research shows that about 0.5% of breastfed babies have CMPA, whereas the number is slightly higher in formula-fed babies, ranging from 2% to 7.5%.

This difference is believed to be due to variations in gut bacteria between breastfed and formula-fed babies. Additionally, the level of cow’s milk protein in breast milk is significantly lower—about 100,000 times lower—than in formula milk.

How do I know if my baby has a milk allergy from my breastmilk?

There are several symptoms of milk allergy that may be seen if you are having dairy products in your diet when breastfeed. These are some of the common things to look out for

  1. Gastrointestinal Issues: Frequent vomiting, diarrhoea, mucous (stringy) stools which may also have blood present. Constipation can also be a symptom of milk allergy.  
  2. Skin Reactions: Eczema (atopic dermatitis), rashes, or hives.
  3. Respiratory Symptoms: Chronic coughing, wheezing, a runny nose or hayfever-like symptoms. 
  4. General Discomfort: Reflux, excessive crying, irritability, or colic-like symptoms.

These symptoms can appear within minutes to a few hours after breastfeeding and the speed or the symptoms would help us to get the correct diagnosis for your baby. 

Non-IgE vs IgE symptoms of CMPA in exclusively breastfed infants.

Understanding the difference between non-IgE and IgE-mediated symptoms of cow’s milk protein allergy (CMPA) is crucial for recognising and getting the correct diagnosis for your baby. It’s also important to remember that symptoms can range for mild to moderate to more severe symptoms as with any food allergy. 

IgE Mediated Symptoms

IgE-mediated symptoms involve the immune system producing immunoglobulin E (IgE) antibodies in response to cow’s milk protein. Your baby may have an immediate reaction to this food or symptoms occur within a short space of time (up to two hours after). 

Common IgE-mediated symptoms include:

  • Skin Reactions: Hives, swelling of the lips, face, or eyes.
  • Gastrointestinal Issues: Immediate vomiting or diarrhoea.
  • Respiratory Symptoms: Wheezing, coughing, nasal congestion, or difficulty breathing.
  • Anaphylaxis: A severe, potentially life-threatening allergic reaction that requires immediate medical attention.

Non-IgE Mediated Symptoms

Non-IgE-mediated CMPA does not involve IgE antibodies and will generally have a delayed onset, with symptoms appearing several hours to days after exposure. These symptoms can include:

  • Gastrointestinal Issues: Blood or mucus in stools, diarrhoea, constipation, or reflux.
  • Skin Reactions: Eczema or persistent rashes
  • General Discomfort: Colic, excessive crying, irritability, or poor growth.

Understanding these differences is essential for identifying the type of allergic reaction your baby may be experiencing and for guiding diagnosis in exclusively breastfed babies. 

Anaphylaxis and Seeking Emergency Attention

Most reactions to cow’s milk protein in exclusively breastfed babies are mild or moderate, with severe forms of milk allergy being very rare. It is thought that immunomodulators (supporting the immune system) present in breast milk and differences in the gut flora of breastfed and formula-fed infants may contribute to this.

Signs of Anaphylaxis to milk

Anaphylaxis is a severe and potentially life-threatening allergic reaction that requires immediate medical intervention. While rare, it is important to recognise the signs and know when to seek emergency attention. Signs of anaphylaxis include:

  • Skin Reactions: Hives, swelling, or a rash that spreads rapidly.
  • Respiratory Symptoms: Difficulty breathing, wheezing, or tightness in the throat.
  • Cardiovascular Issues: Rapid heartbeat, a drop in blood pressure, or lethargy.
  • Gastrointestinal Symptoms: Severe vomiting, diarrhea, or abdominal pain.
  • General Symptoms: Anxiety, confusion, or a sense of impending doom – more so in adults. 

Immediate Actions to Take

If you suspect your baby is experiencing anaphylaxis to milk protein 

  1. Administer Autoinjector; If you have an epinephrine auto-injector; this may be a brand called epipen or jext, use it immediately according to the instructions.
  2. Call Emergency Services: Dial emergency services immediately. 

Even if symptoms seem to improve after administering, it is crucial to seek medical attention, as further treatment and observation may be necessary. Anaphylaxis can have a biphasic pattern, with symptoms returning after the initial episode.

Diagnosis of CMPA in exclusive breastfeeding

Diagnosing cow’s milk protein allergy (CMPA) in breastfed babies involves a combination of medical history, symptom observation, and sometimes, elimination diets and testing. This is dependent on the speed of symptoms. 

Here are the steps typically involved in the diagnosis process:

Medical History and Symptom Review

The first step is to discuss your baby’s symptoms and medical history with a healthcare professional, usually in primary care. You can use my symptom tracker to support you with this. There are some important things to make sure that you include; 

  • What are your baby’s symptoms and how soon they occur. 
  • Any family history of allergies or atopic conditions such as asthma or eczema. 
  • The baby’s diet and any potential exposure to cow’s milk protein through breastmilk.

It is important to be aware that not all babies who are breastfed will show the symptoms of milk allergy from birth. Some babies will start with symptoms when solid foods are introduced into their own diet. 

CMPA & Breastfeeding

Elimination diet for Non IgE milk allergy

If milk allergy is suspected, your dietitian or another qualified health professional should recommend an elimination diet or ‘milk challenge’.  This involves:

  • Dietary exclusion of all cow’s milk products from your diet for a period of 2-4 weeks. This includes foods such as milk, cheese, butter, yogurt, chocolate and ice cream. 
  • Observing if the baby’s symptoms improve during this time.

If symptoms improve, the next step may be a “re-challenge” where cow’s milk protein is reintroduced into your diet to see if symptoms return. This should always be done under medical supervision to ensure safety and also nutritional balance. 

If symptoms aren’t relieved when you do an elimination diet or ‘milk challenge’ then they are not due to milk allergy and I would advise you to speak with your health care provider for more support. 

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

Allergy Testing for IgE Allergy

If it is suspected that your baby has an IgE immune response to your breastmilk then a milk challenge is not appropriate and in some cases, allergy testing may be recommended. 

There are two main types of allergy testing used;

  • Skin Prick Test: Small amounts of potential allergens are introduced into the skin to see if there is a reaction to this food. 
  • Blood Tests: These can measure the presence of specific IgE antibodies to cow’s milk protein.

However, it’s important that an allergy focussed history has also been taken to ensure that your baby has definitely had immediate symptoms to milk protein before carrying out these tests. 

CMPA foods to avoid when breastfeeding

If your baby has been diagnosed with a cow’s milk protein allergy (CMPA), it is essential to eliminate all sources of cow’s milk protein from your diet while breastfeeding. Here are key foods and ingredients to avoid:

Dairy Products

  • Milk: All forms, including whole, skim, evaporated, and powdered.
  • Cheese: All types, including hard cheeses, soft cheeses, and processed cheese products.
  • Butter and Margarine: Unless labelled dairy-free or specifically free from cow’s milk protein.
  • Yogurt and Kefir: Both regular and Greek varieties.
  • Cream: Including sour cream, heavy cream, and whipped cream.
  • Ice Cream and Gelato: Any dairy-based frozen desserts – check out my blog on dairy free gelato for some great options to try. 
  • Custards and Puddings: Made with milk or cream.

Processed Foods

Many processed foods contain hidden dairy ingredients. Be cautious with:

  • Baked Goods: Breads, cakes, cookies, and pastries often contain milk or butter.
  • Sauces and Dressings: Some contain cream, butter, or cheese (e.g., Alfredo sauce, ranch dressing).
  • Soups and Broths: Cream-based soups and some broths may have dairy.
  • Snack Foods: Certain crackers, chips, crisps and protein bars may include milk derivatives.
  • Processed Meats: Some sausages and deli meats contain milk protein as a filler.

Ingredients to Watch For

Carefully read food labels and avoid products containing:

  • Casein
  • Whey
  • Lactose
  • Caseinate (e.g., sodium caseinate)
  • Ghee
  • Lactalbumin
  • Lactoglobulin

Hidden Sources of Dairy

Dairy can also be hidden in non-food products and cross-contamination can occur, so be mindful of:

  • Certain medications and supplements: Some might contain milk protein.
  • Non-dairy creamers: Some contain casein derivatives. 
  • Energy and protein drinks: Check for whey protein and other dairy ingredients.

Plant based alternatives and Nutritional Balance

Replacing dairy in your diet is crucial to ensure you and your baby get adequate nutrition. Consider alternatives like:

  • Milk Alternatives: Almond milk, soy milk, oat milk, and other plant-based milks. Make sure these have added calcium (120mg per 100mls)
  • Dairy-Free Cheese and Yogurt: Look for products labeled free from milk protein. 
  • Plant-Based Butter and Margarine: Ensure they are labeled dairy-free.

What does ‘may contain’ milk mean?

What does may contain milk mean?

If you see this on a product this means that this product has been produced in a factory where other products containing milk. This means that the manufacturer may use the same equipment to make different products. Even after cleaning this equipment, they cannot guarantee that the equipment is 100% clear and therefore will label the product as ‘may contain milk’. 

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
CMPA Breastfeeding – The Milk Challenge

CMPA & Breastfeeding Summary

So, yes, breastfed babies can have a milk allergy, but it’s crucial to ensure the correct diagnosis if cow’s milk protein allergy (CMPA) is suspected. Diagnosis often involves a milk challenge, especially in non-IgE (delayed) milk allergy cases. Your baby may need a referral to a specialist allergy team if they require allergy testing. 

And finally, don’t let anyone tell you that you have to stop breastfeeding if your baby has a milk allergy – this is not true and can be frustrating to hear! With additional support, including guidance on essential nutrients and modifications to a mother’s diet, you and your baby can still receive all the necessary nutrition while following a strict milk-free diet. If you need further assistance or information, feel free to contact me.

CMPA Breastfeeding

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

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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