Cow's milk protein-induced colitis in the breast-fed infant.

A 3-month-old boy is described who developed an inflammatory proctocolitis during exclusive breast feeding. The major symptom was bloody diarrhea. No growth failure or constitutional symptoms were present. Bacterial, viral, and parasitic infection was excluded. The colonoscopic findings of focal ulceration, edema, and increased friability and the histologic picture with a marked eosinophilic infiltration were indicative of an allergic intestinal reaction. The infant responded favorably to the withdrawal of the mother's milk and the initiation of hydrolyzed casein formula. The challenge with cow's milk led to a clinical relapse resembling the initial manifestation.