Allergy to cow's milk is one of the most common food allergies in childhood and affects about 1-2% of preschool children. Most children grow out of it by the age of 3-5 years — less than 0.1% of school age children have cow's milk allergy. True allergy to cow's milk is rare in adults.

Cow's milk allergy is often due to an immune system reaction against milk proteins. Exposure to even a trace amount of milk protein can be a problem for someone with milk protein allergy.

Symptoms of allergy to cow's milk may include a rash (eczema or hives), swelling, abdominal pain or vomiting, diarrhoea or breathing difficulties.

Anaphylaxis is the most severe allergic reaction and requires immediate treatment. Symptoms include difficulty/noisy breathing and swelling of the tongue. If you think someone is having an allergic reaction, seek medical advice urgently as symptoms can worsen rapidly. If breathing is affected, call triple zero (000).

Diagnosis of cow's milk allergy is often obvious when symptoms occur within minutes of exposure. Skin prick allergen tests from your doctor may also help. When symptoms are delayed, cow's milk allergy can be harder to diagnose.

Lactose in cow's milk is a problem for people who lack the enzyme lactose, but this is different to cow's milk allergy.

Choosing Wisely and allergen testing

The Australasian Society of Clinical Immunology and Allergy recommends you should speak to your doctor or specialist about the benefits and safety of allergen immunotherapy or before attempting any allergy testing or treatment. For further information, visit the Choosing Wisely Australia website.

Follow the links below to find trusted information about allergic reactions to cow's milk.