What is Cow's Milk Protein Allergy?

What is Cow's Milk Protein Allergy?

Cow's Milk Protein Allergy (or CMPA) is an allergic reaction to one or more of the proteins in cow's milk (or foods that contain cow's milk) . There is a very high likelihood of cross-reactivity between cow's milk protein and the proteins in goat's or sheep's milk (and other mammalian milk), which means that if a person has an allergy to one of these foods then they are likely to have an allergic reaction to the other/others (1).

What about Soy?

Some people who react to the proteins in cow's milk will have cross-reactivity with soy, therefore it is commonly recommended that little ones, or mothers that are breastfeeding a little one with Cow's Milk Protein Allergy, also need to avoid soy foods/products in their diets (2).

How common is cow's milk protein allergy and when does it usually start?

Cow's Milk Protein Allergy is the most common food allergy in little ones, with up to 3% of children diagnosed by their 1st birthday (3, 4, 5). While very prevalent, one of the positive things about Cow's Milk Protein Allergy is that 80% of children will outgrow their Cow's Milk Protein Allergy by age 5 (1). An allergy can begin at any stage of life, however, Cow's Milk Protein Allergy often occurs in infants and young children.

What foods contain cow’s milk protein?

Some examples of common foods that contain cow’s milk protein are dairy foods like cow’s milk, butter, yoghurt, cheese, cream, cow’s milk-derived infant formula, ghee, whey/casein protein powders, ice cream*.

Some examples of foods that are very likely to contain cow’s milk protein are margarine, pasta sauces, chocolate, breakfast cereals, bread, infant biscuits or rusks, potato products, processed meats, salad dressings, snack foods, baked goods, pastry items*.

*This is not a complete list of foods that contain or may contain cow’s milk protein, just some examples. It is important to note that any food could contain cow’s milk protein -it depends on the manufacturer, therefore, if your little one has CMPA it is very important to check the ingredients list of every product to check for milk products. In many countries, common allergens will be stated or highlighted in bold.

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What are the symptoms of cow's milk protein allergy?

There are many different symptoms of cow's milk protein allergy and these symptoms can vary greatly in severity. Usually, the symptoms of Cow's Milk Protein Allergy will occur two or more hours after consuming cow's milk protein, however, in some cases, symptoms can also be immediate and life-threatening.

These can be categorised into two types of reaction:

IgE-Mediated Cow's Milk Protein Allergy (or Rapid Onset Cow's Milk Protein Allergy )

Rapid onset Cow's Milk Protein Allergy reactions will usually occur within 15 minutes (but sometimes up to 2 hours after consuming cow's milk protein)

Symptoms include one or more of the following:

Mild or moderate:

  • Hives
  • Swelling of the lips, face, or eyes
  • Stomach pain
  • Vomiting
  • Diarrhoea

Severe allergic reactions (Anaphylaxis):

  • Noisy breathing or wheeze
  • Swelling and or tightness of the tongue or throat
  • Hoarse voice
  • Loss of consciousness
  • Floppiness in babies or young children.

Anaphylaxis is a medical emergency and requires immediate treatment.

Non-IgE mediated Cow's Milk Protein Allergy (or Delayed Onset Cow's Milk Protein Allergy)

Delayed reactions to cow's milk protein occur two or more hours after consuming cow's milk protein foods and are usually in the gastrointestinal tract such as vomiting, diarrhoea, and bloating.

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Symptoms include one or more of the following:

  • Exacerbated eczema
  • Delayed vomiting
  • Delayed diarrhoea
  • Faltering growth
  • Blood or mucous in the stool (1)

Please note: these symptoms are not exclusive to Cow’s Milk Protein Allergy, it is important to have any of these symptoms checked by your medical doctor.

Diagnosis is very important!

It is very important to have a suspected Cow’s Milk Protein Allergy diagnosed by a medical doctor as cow's milk and dairy foods can often provide a large proportion of the calcium in a person's diet and it is integral that this is managed with support from a qualified health professional (such as a Doctor or Dietitian) to prevent calcium deficiency which can lead to diseases like osteoporosis in adults or rickets in children. If your little one is formula-fed or mix-fed it is important that your doctor can assess them and recommend or prescribe an appropriate formula based on their growth, gender, allergy severity, type of allergy, etc.

What about lactose intolerance?

Lactose intolerance and Cow’s Milk Protein Allergy are not the same thing. Lactose intolerance is not an allergy to the proteins in cow's milk, it is an intolerance to the sugar ‘lactose’ found in cow's milk. Some people have lower levels of/or lack the enzyme lactase which helps to break apart this sugar. Lactose is a disaccharide, meaning it's composed of two sugar units (glucose and galactose), only single sugar units will be absorbed across the gut wall, so if there isn't enough lactase to break the sugars apart then the lactose will not be broken apart and will consequently not be absorbed. When not absorbed lactose can stay in the gut, this can lead to symptoms like diarrhoea, flatulence, pain, and distention (bloating) (6). Lactose intolerance can often be resolved by swapping regular dairy products for lactose-free dairy products.

Can someone with cow’s milk protein allergy have lactose free or A2 dairy products?

No. Lactose-free and A2 products contain milk proteins.

Lactose-free products have just had the enzyme lactase added to them to break down the sugar part of the milk, this does not mean that the proteins (which cause an allergic reaction) have been removed.

Regular milk contains both the A1 and A2 proteins, whereas A2 milk contains only the A2 protein, this may help with digestion for some people but is NOT appropriate for those with Cow's Milk Protein Allergy as A2 milk still contains the milk proteins present in regular cow's milk, just not the A1 beta-casein.

If a little one has cow's milk protein allergy can they have plant-based drinks instead?

It depends on their age and growth. Plant-based beverages (which are not technically milk but are often referred to as ‘milks’ or ‘mylks’) are not nutritionally adequate as a drink for little ones under the age of 12 months old as they do not contain enough or the right amounts of vitamins, minerals, and macronutrients (carbohydrates, proteins, and fat) to replace breast milk or formula* (this excludes plant based infant formulas that have been recommended by a medical professional). Sometimes plant-based infant formula like soy formula may be recommended by a doctor but it is important to speak to a doctor before swapping to a plant-based formula as this will depend on the individual needs of the person (7).

After 12 months it depends on your little one's growth and what the recommendations are in your country (some countries have fortified plant-based milk that has been developed specifically for little ones aged between 1 and 2 years, however, it is integral that a medical doctor is consulted before swapping an infant from breastmilk or formula to a plant-based milk before the age of 2 years old as plant-based milk is often lower in protein and energy which can greatly impact a little one's growth (8).

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What is the difference between CMPA and CMPI?

CMPI stands for Cow's Milk Protein Intolerance and this definition can vary to mean:

Both IgE mediated and non-IgE mediated Cow's Milk Protein Allergy


Just Non-IgE mediated Cow's Milk Protein Allergy

It is important to clarify this with your doctor.

Are there any risk factors for cow’s milk protein allergy?

If an infant has severe eczema and or an immediate family (sibling or parent) history of allergies then they are considered to be at an increased risk of developing a food allergy (9).

When should I contact my Doctor?

If you are concerned that your little one may have a Cow’s Milk Protein Allergy or notice any of the symptoms of Cow’s Milk Protein Allergy in your little one you should speak to your medical doctor as soon as possible. If you notice that your little one is experiencing severe and/or rapid onset symptoms after consuming cow's milk or foods that contain cow's milk you should seek immediate medical attention.

Disclaimer: The information in this article is provided for information purposes only and is not intended to replace advice from your doctor or other registered health professional. The information and materials in this article are not intended to constitute a comprehensive guide concerning all aspects of treatment. All readers are urged to always seek advice from a registered health care professional for diagnosis and answers to their medical questions and to ascertain whether the particular information described in this article is suitable in their particular circumstances.


  1. Australasian Society of Clinical Immunology and Allergy (ASCIA). (2019). Cow's Milk (Dairy) Allergy. Retrieved from https://www.allergy.org.au/patients/food-allergy/cows-milk-dairy-allergy
  2. The Royal Children’s Hospital Melbourne. (2013). COWS MILK AND SOY ALLERGY. Retrieved from https://www.rch.org.au/uploadedFiles/Main/Content/allergy/RCH_Cows%20milk%20and%20Soy%20allergy.pdf
  3. Rona, R. J., Keil, T., Summers, C., Gislason, D., Zuidmeer, L., Sodergren, E., ... & Madsen, C. (2007). The prevalence of food allergy: a meta-analysis. Journal of Allergy and Clinical Immunology, 120(3), 638-646.
  4. Bock, S. A. (1987). Prospective appraisal of complaints of adverse reactions to foods in children during the first 3 years of life. Pediatrics, 79(5), 683-688.
  5. Bock, S. A. (1987). Prospective appraisal of complaints of adverse reactions to foods in children during the first 3 years of life. Pediatrics, 79(5), 683-688.
  6. Swagerty Jr, Daniel L., Anne Walling, and Robert M. Klein. "Lactose intolerance." American family physician 65.9 (2002): 1845.
  7. Verduci, E., D’Elios, S., Cerrato, L., Comberiati, P., Calvani, M., Palazzo, S., ... & Peroni, D. G. (2019). Cow’s milk substitutes for children: Nutritional aspects of milk from different mammalian species, special formula and plant-based beverages. Nutrients, 11(8), 1739.
  8. Food Standards Australia & New Zealand. (201). Plant-based milk alternatives. Retrieved from https://www.foodstandards.gov.au/consumer/nutrition/milkaltern/Pages/default.aspx
  9. Australasian Society of Clinical Immunology and Allergy (ASCIA). (2020). Infant Feeding and Allergy Prevention Clinical Update. Retrieved from https://www.allergy.org.au/hp/papers/infant-feeding-and-allergy-prevention-clinical-update
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