Milk Protein Intolerance


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Milk protein intolerance, also commonly referred to as casein intolerance occurs when the body produces an adverse reaction to a protein found in milk. This protein is called casein. The name milk protein intolerance can be misleading and often cause confusion. Although it is named a food intolerance, it is more like an allergy. This is due to the involvement of the immune system. For those who are casein intolerant, when casein is eaten the body’s immune system detects the presence of the protein and tries to destroy it. This leads to the release of histamine as part of the immune response, causing a wide array of unpleasant symptoms.

What is casein?

Casein is a type of protein. It is typically the most abundant protein found in the different types of mammalian milk. The most popular commercially available mammalian milk comes from cows and goats. Both of which are used widely in the manufacture of processed food.

What causes it?

Casein intolerance or milk protein intolerance is caused by the adverse response to casein, by the body’s own immune system. This triggers the a variety of unpleasant symptoms to include – vomiting and fatigue.

Milk protein intolerance is more common in babies rather than adults; this is due to the babies developing immune system. Babies have an immature immune system which can sometimes attack foreign proteins such as milk protein. It is even more likely in infants where there is a family history of milk protein intolerance. Milk protein intolerance is very rare in babies fed only on breast milk. Although, if the mother has consumed milk protein it can be passed to the baby through the breast milk and so cause milk protein intolerance symptoms. The majority of milk protein intolerant infants are those that have been fed infant formula, as infant formula often derived from milk protein.

Usually, milk protein intolerance does not persist after 4 years of age. At this point the infant’s immune system is more developed and the milk protein should not trigger the release of histamine.


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