Adult onset of cow's milk protein allergy with small-intestinal mucosal IgE mast cells

We report a female patient with adult onset of cow's milk protein allergy. For 1 year, she experienced repeated gastrointestinal symptoms and had a single exercise-induced anaphylactic reaction. In addition to positive skin tests and specific IgE to milk proteins and a positive challenge test, immunohistochemistry of the small intestine showed a marked increase of IgE-positive mast cells. This finding is highly specific and could provide an additional tool for diagnosing cow's milk protein allergy and possibly also other food allergies.