What is cow’s milk protein allergy?

One of the most common food allergies seen in the first year of a baby’s life, cow’s milk allergy, occurs when the immune system reacts negatively to the protein found in cow’s milk. It is not to be confused with lactose intolerance, which is a digestive inability to break down lactose. These milk proteins are usually transferred from the mother while breastfeeding, or from formulas and other supporting foods that contain cow’s milk protein.

Reactions from cow’s milk vary in timing, ranging from immediate or early reactions to delayed or late reactions. Early reactions often occur minutes to hours after exposure, whereas a late reaction will not show symptoms until 48 hours or even a week later after initial digestion.

Most children outgrow CMA by 3-5 years of age, but some remain allergic into their later years. It is important to be aware of the allergy’s severity, as an anaphylactic reaction to cow’s milk can be life-threatening and requires immediate medical attention. No case of CMA should be treated lightly in children as the signs and symptoms can be very uncomfortable for them.

What are the signs and symptoms of cow’s milk allergy?

Statistics show that 2% of the Australian and New Zealand population of infants are allergic to cow’s milk; that’s as much as 1 in 50. Despite these high numbers, it can be difficult to accurately diagnose the signs and symptoms of an allergic reaction to cow’s milk. That is because these symptoms occur differently in many infants, with some showing a higher inclination to early dermatological reactions, while others have late gastrointestinal reactions.

Most infants experiencing a reaction to cow’s milk allergy will show signs of distress through insomnia and crying, but symptoms may also manifest through dermatological, gastrointestinal and respiratory signs.


When it comes to reactions to a cow’s milk allergy in children, a dermatological reaction is fairly common. Ingestion of cow’s milk, no matter how mild, can cause visible changes in an infant’s complexion, including:

  • Swelling of face, lips and eyes
  • Raised red bumps of skin, also known as hives
  • Dermatitis or eczema, characterised by itchy, red, weeping crusty rashes on the skin
  • Rashes
  • Itchy or watery eyes


Cow’s milk allergy typically begins to show signs of a reaction once ingestion has occurred. This can result in gastrointestinal symptoms that may range from mild stomach aches to more severe allergic reactions like blood in the stools. Other symptoms include:


Respiratory reactions are more often seen in a serious allergic reaction to cow’s milk, but a child may also show one or more of the following in a mild reaction:

  • Noisy breathing or wheezing
  • Swelling or tightness in the throat
  • Runny nose and sneezing
  • Chronic cough

Signs of anaphylactic shock may be a sign of a severe allergic reaction. Medical attention should be sought out immediately if a child is showing signs like:

  • Paleness of skin
  • Laxity of body
  • Difficulty breathing or wheezing
  • Inability to talk or make sounds
  • Persistent dizziness
  • Throat or tongue swelling

Take action and call the nearest medical emergency facility if you notice a child is entering anaphylactic shock or is having a life-threatening reaction.

Cow’s milk allergy diagnosis

Before attempting a medical diagnosis, you must collect a record of the affected child’s symptoms. This way you have the full picture of the child’s reactions and the time between ingestion and signs of symptoms. In the case of early reactions after consuming cow’s milk or dairy foods, it will be easier to diagnose the allergy, but later reactions may take more time and effort.

You may be able to test for allergies or refer the patient to an allergist. Either way, there are some common allergy tests to get a cow’s milk allergy diagnosed. These include:

  • A skin prick test: A small amount of cow’s milk will be dropped onto the skin, which is then pricked to expose your immune system to the allergen. The skin will show signs of a reaction in the affected area if the child has an allergic reaction to cow’s milk.
  • Blood tests: If a skin prick test is not suitable, a blood test may be conducted. This is usually in the case of the child having a severe allergic reaction in the form of eczema, or they are taking medications that may interfere with the testing.
  • Elimination diet: This involves ensuring the child’s diet has no cow’s milk in it. After they avoid milk for some time, the parents are directed to slowly introduce cow’s milk and milk-based products back into their child’s diet.

Other uncommon allergy tests include:

  • Intradermal skin testing
  • Patch testing
  • Oral allergen testing

Managing mild-to-moderate Cow’s milk allergy

Cow’s milk allergy management takes an individualised approach that considers the patient’s age, medical history, symptoms, and severity of allergy to avoid complications and ensure optimal health outcomes.

It is also important to educate patients and their families about the potential for cross-contamination, hidden sources of milk in foods, and how to read allergen labelling.

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