Cow's Milk Allergy with Severe Eosinophilia.

Because the role of eosinophils in neonates is not well understood, the clinical significance of eosinophilia in neonates is unclear. We encountered a rare case of cow's milk allergy in a premature male infant with severe eosinophilia in the neonatal period. The peripheral blood eosinophil count in this infant was 7,404/μL at birth, and he produced stools with fresh blood immediately after birth and prior to the first feedings with regular cow's milk. Although the patient's eosinophil count normalized without specific treatment within 6 weeks after birth, it is possible that the causes of the eosinophilia in this infant prior to the first feedings with regular cow's milk were different from those after the first feedings. Cow's milk allergy was diagnosed on the basis of the patient's positivity for this allergy in the challenge test and subsequent allergen-specific lymphocyte stimulation test performed at 6 months of age.