Allergic colitis presenting in the first day of life: report of three cases.

Allergic colitis can occur within hours of birth and should be considered in the differential diagnosis of any newborn in whom hematochezia develops. This diagnosis should be considered after excluding infectious and anatomic disorders common to this age group. The diagnosis is supported by the healthy appearance of affected infants and specific proctosigmoidoscopic and histopathologic findings. Infants with allergic colitis usually respond to withdrawal of the offending antigen, by the use of hydrolyzed cow's milk protein formula or more elemental formulas, or if the infant has been breast fed, by the strict removal of the offending antigen from the breast-feeding mother's diet.