In allergic proctocolitis, the most common gastrointestinal symptom is the development of bloody stools. This usually occurs between 2 and 6 weeks of age,6 although some have reported symptoms beginning as early as the first day of life. Dietary proteins excreted in the mother’s milk are responsible for the majority of cases and induce an inflammatory response of the rectum and distal sigmoid colon referred to as allergic proctocolitis. It should be emphasized that breastfed infants with allergic proctocolitis are generally ‘‘well appearing’’ other than the presence of blood within the stool. Blood loss is typically modest but can occasionally produce anemia and/or hypoalbuminemia. In very rare cases, symptoms may lead to failure to thrive. Systemic manifestations such as emesis, dramatic diarrhea, or abdominal distention are rare and may suggest other allergic disorders of the gastrointestinal tract.