Interesting facts about cow’s milk allergy

Cows’ milk allergy (also known as cow’s milk protein allergy) is a relatively common food allergy in babies and young children1. Here, we answer some frequently asked questions about this condition.

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What is cow’s milk allergy?

Cow’s milk allergy is an allergic reaction to the protein in cow’s milk2. Cow’s milk allergy can affect both formula-fed and breast-fed babies, since an allergic baby can detect the cow’s milk protein in the mother’s diet through her breast milk3. Symptoms can take place right after feeding, or can be delayed for up to a couple of days3.

How common is cow’s milk allergy?

Cow’s milk allergy is the most common type of food allergy in infants, affecting between 2% and 5% of babies and young children1. It usually develops before one year of age, and most children will grow out of it by age 5, when they might reintroduce cow’s milk into their diet1. It is not clear why some children develop food allergies such as cow’s milk allergy, or why some grow out of their condition whilst some remain allergic; however, rates of food allergy are increasing globally, particularly in young children4.

What causes cow’s milk allergy?

The role of our immune system is to protect our bodies against infections by attacking the viruses and bad bacteria {‘pathogens’) that can make us ill5,6. In a food-related allergic reaction, the immune system overreacts to a protein that is usually harmless (e.g. a peanut allergy is a reaction to the protein in peanuts) 5,6.

In cow’s milk allergy, the body's immune system reacts to the protein in cow’s milk, mistaking it for a harmful pathogen. When an allergic infant consumes cow’s milk or something that contains cow’s milk protein, their immune system has an allergic reaction.

What are the symptoms of cow’s milk allergy?

Common symptoms of cow’s milk allergy fall broadly into three categories7-10:

  • Digestive symptoms, e.g. vomiting, diarrhea, and reflux
  • Respiratory symptoms, e.g. asthma-like symptoms such as wheezing and coughing
  • Skin problems such as rashes, hives or eczema, which may take up to 3-5 days to appear

Colic (excessive crying) is also known to be a symptom of cow’s milk allergy.

Allergic symptoms can happen immediately after feeding (e.g. severe breathing problems or vomiting) or be delayed by hours or days.

The symptoms of cow’s milk allergy are wide-ranging and non-specific – meaning they are also found in many other conditions. A diagnosis of cow’s milk allergy should always be made by a qualified healthcare professional.

Is cow’s milk allergy the same as lactose intolerance?

Cow’s milk allergy and lactose intolerance are not the same. Although both are reactions by the body triggered by cow’s milk, an allergy and an intolerance are actually very different11.

  • An allergy is caused by an incorrect response by the immune system to an otherwise harmless substance, such as cow’s milk protein2.
  • Lactose intolerance in a baby means their body doesn’t produce enough lactase enyzme (enzymes help breakdown food) to help digest lactose – the naturally occurring sugars found in milk12. A baby with lactose intolerance can drink a lactose-free formula milk.
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While digestive symptoms can be found in both cow’s milk allergy and lactose intolerance, lactose intolerance does not usually affect the skin or the respiratory system11.

Which factors can increase a baby’s risk of developing CMA?

A family history of allergy (including eczema, hay fever or asthma) increases the risk of a baby developing a food allergy2. However, even babies with no family history of allergy can develop cow’s milk allergy; a baby’s environment can affect the likelihood of developing an allergy13-15.

Bacteria and other microorganisms (collectively known as the ‘microbiota’) in the gut have a role in the healthy functioning of the body, including the immune system16. When the delicate balance of the gut microbiota is disrupted and the number of bad bacteria outweighs the good bacteria (‘gut microbiota dysbiosis’), the immune system can start to react incorrectly to harmless things, such as milk protein5,6.

Gut microbiota dysbiosis is linked to an increased risk of food allergies, including cow’s milk allergy. 14-16 Specifically, infants with food allergies appear to have fewer good bacteria in their gut compared with healthy, breastfed infants17-19.

Things that can upset the balance of the gut microbiota include:

  • Repeated courses of antibiotics during infancy, which can kill both bad bacteria and good20.
  • Exposure to pollution21,22
  • C-section delivery: babies who are born vaginally come into contact with beneficial bacteria that C-section infants are not exposed to23

Gut health can be improved by good nutrition and consumption of prebiotics and probiotics24.

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How is cow’s milk allergy diagnosed?

It is important that cow’s milk allergy is correctly diagnosed by a healthcare professional so that appropriate management can be initiated. 

Diagnosing cow’s milk allergy can take a lot of time and visits to the doctor25, as some symptoms are also fairly common to non-allergic babies, or those with an intolerance.

Delayed diagnosis can be distressing for babies and their parents and can potentially harm a baby’s growth and development25.

Diagnosis by a healthcare professional is made based on symptoms, medical history and if necessary, baby allergy testing. An elimination diet – where certain foods are removed from the mother’s diet when breastfeeding, or a baby’s diet under the doctor’s guidance – may also be used to aid diagnosis26.

If you think your child or baby is allergic to milk, talk to your healthcare professional.

How can CMA be managed?

Breastfeeding is the very best nutrition for all infants. However, very sensitive babies can have allergic reactions to even small traces of cow’s milk protein found in breast milk.

If a baby is suspected to have a cow’s milk allergy, a healthcare professional may advise breastfeeding mothers to eliminate all products containing cows’ milk from their diets27. Always talk to a dietician / healthcare professional before making dietary changes.

When breastfeeding plus an elimination diet are not possible, there are hypoallergenic formulas specially designed for babies with cow’s milk allergy. Some contain cow’s milk protein, but the proteins are broken down until they are too small to cause an allergic reaction. Others contain no cows’ milk protein at all (for infants with severe cow’s milk allergy28. Symptoms usually disappear once what is causing the allergy is identified and removed from the baby’s diet27,28

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How does cow’s milk allergy impact infants?

The symptoms of cow’s milk allergy are wide-ranging and non-specific. Many parents can wait months for their baby to be diagnosed with cow’s milk allergy (also known as cow’s milk protein allergy) [30]. Learn more about signs and symptoms of cow’s milk allergy and what to expect when a doctor is investigating a possible cow’s milk allergy.

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Allergy is on the rise

Cow’s milk allergy is one of the most common childhood allergies, affecting up to 5% of infants and children [31]. Beyond the clinical symptoms, allergy can have a major impact on the quality of life of patients and their families, as well as being an ongoing economic burden on healthcare services [32-35].