Milk allergy in the neonatal intensive care unit: comparison between premature and full-term neonates

BACKGROUND There have been several reports on neonates with milk allergy in a neonatal ward. This type of allergy is mostly categorized as a non-IgE-mediated food allergy. Although most cases of milk allergy occur in the first few months of life, the differences in clinical characteristics between premature and full-term neonates are still unclear. OBJECTIVE This study aimed to clarify the differences in clinical characteristics of milk allergy between premature and full-term neonates. METHODS We retrospectively evaluated 2,116 neonates admitted to the Department of Neonatology, Chiba Kaihin Municipal Hospital, between 2001 and 2007. RESULTS We identified 24 neonates strongly suspected of having milk allergy because of symptoms, such as bloody stools, repeated vomiting, diminished sucking and abdominal distension, as well as objective laboratory findings of eosinophilia in stool cytology and/or positive results for a rectal milk challenge test. Twelve of these 24 neonates were premature (median gestational age, 31 ± 3 weeks; median birth weight, 1,656 ± 592 g) and the other 12 were full-term (median gestational age, 38 ± 1 weeks; median birth weight, 2,760 ± 560 g). There were no differences in symptoms and time to start of feeding between premature and full-term neonates, but there was a significant difference in the median postnatal age at onset (premature neonates: 23 days; vs. full-term neonates: 3.5 days; p < 0.01). CONCLUSION All premature neonates developed a milk allergy after 32 weeks of corrected gestational age, suggesting that the development of milk allergy requires a certain degree of immunological maturation.