What Is Cow’s Milk Protein Allergy?

The allergen in a cow’s milk allergy is cow’s milk protein.

In infants, the digestive tract is not yet fully developed. There is an insufficient secretion of digestive enzymes, and the pH level in the intestines is relatively high—conditions that hinder the proper digestion of proteins. As a result, a larger amount of protein remains incompletely digested; these undigested proteins can pass through the intestinal lining and enter the bloodstream, triggering an allergic reaction.

Furthermore, because an infant’s digestive tract may lack a protective layer—typically formed by a thriving population of beneficial bacteria (probiotics)—or because the intestinal lining itself is not yet fully developed, there may be significant gaps between the epithelial cells. This makes it easier for intact proteins or large protein fragments to penetrate the mucosal barrier, come into contact with antibodies in the bloodstream, and subsequently trigger an allergic reaction.