Rectal bleeding is a problem commonly seen in the ambulatory pediatric setting. It can be a terrifying finding for caretakers, sometimes heralding significant pathology. Fortunately, most cases of rectal bleeding in children are due to etiologies that have little morbidity. Rectal bleeding was identified as the chief complaint in 0.3% of all visits presenting to a busy urban emergency department over a 10-month period. Only 4% of affected patients manifested potentially life-threatening conditions. After birth the gut mucosa is challenged by a myriad of antigens, from viruses to commensal microbiota and dietary antigens. Although controlled in the mature gut, these antigens may induce inflammation in the developing gastrointestinal tract. Several etiologies have been suggested for IRB. In the past, the most common etiology was believed to be a hypersensitivity reaction of the bowel mucosa to digested antigens, primarily to the protein in cow?s milk. Studies conducted in the late 1990s showed that eliminating cow?s milk from an infant?s diet was followed by cessation of the bleeding. However, reintroducing cow?s milk into infants? diets did not result in recurrence of the bleeding.
Studies aimed at evaluating the involvement of allergic mechanisms among infants with rectal bleeding have shown varying results. More recent studies have demonstrated a relatively low rate (12.5 to 18%) of evidence to support allergic colitis among infants with IRB. These studies found IRB to be a benign and self- limiting phenomenon whose cause is mostly unknown. Still, some of the infants who have experienced an IRB event are given specific dietary restrictions that might impair their childhood nutrition. The long-term incidence of allergic clinical signs among these infants has not been evaluated extensively. Dietary protein induced eosinophilic proctocolitis in exclusively breast fed infants is rarely taken into consideration as a cause of rectal bleeding in the neonatal period or early infancy. Failure to appreciate this entity may lead to inappropriate diagnostic or therapeutic intervention. 
IRB in otherwise asymptomatic babies is often observed in neonatal departments. In such cases, most nurseries perform a routine screen for bacterial infection, including white blood cell count, blood and stool cultures, and abdominal radiograph. Feeding is discontinued and antibiotic treatment is given regardless of the baby?s un alarming appearance and normal laboratory and radio- graphic findings. The elimination of cow?s milk antigens from the diet of infants with rectal bleeding or from the diet of the lactating mother is a commonly used and recommended practice, although it seems effective for only some patients.