Cow's milk allergy: a new understanding from immunology

Because of the high prevalence of cow's milk allergy as one of the most frequent clinical presentations of food allergy in infancy and early childhood, it is important to define the condition accurately. Allergy must be distinguished from the broader term food intolerance, which may be defined as a reproducible adverse reaction to the ingestion of a food or to any of its components, ie, proteins, carbohydrates, fats, and additives, and which includes toxic, metabolic, and allergic reactions. By contrast, food allergy may be defined as an adverse clinical reaction to a specific food component and that is immunologically mediated. The rapid increase in knowledge resulting from research in immunology in recent years has not only led to a better understanding of the basis for cow's milk allergy in infancy, but has also yielded considerable promise for improved diagnosis and management of the condition.

To review recent developments in immunology which demonstrate how they may lead to a better understanding of the clinical spectrum of cow's milk allergy in infants and children.

English language articles were selected from PubMed and selected abstracts that would have immediate, practical clinical implications. The review focuses on themes related to gastro-enterology, focusing upon the esophagus and small intestine.

In cow's milk-sensitive esophagitis, there is dense infiltrate of eosinophils and increased T cell activation with upregulation of the chemokine eotaxin. In cow's milk-sensitive enteropathy, there is T cell activation, and it often results as a sequela of gastro-enteritis. Changing patterns in recent years suggests that sensitization occurs via mother's breastmilk to cow's milk and multiple food antigens. There is evidence of reduced Th1 response in these children. This is related to associated IgA deficiency and low levels of cytokine transforming growth factor beta.

The results of the present review demonstrate that the clinical manifestations of cow's milk allergy are very diverse, with differences between developing and developed countries. Understanding the immunologic mechanisms is of key importance in understanding this diversity.