Peripheral blood eosinophilia in infants at 3 months of age is associated with subsequent development of atopic disease in early childhood.

BACKGROUND: We tested the hypothesis that eosinophilia in peripheral blood and nasal mucosa of infants is an early sign of allergic disease.
METHODS: The appearance of eosinophilic leukocytes in peripheral blood and nasal mucosa was studied prospectively in 67 infants up to 18 months of age, with or without a family history of atopy.
RESULTS: Eosinophilia was associated with simultaneous presence or subsequent development of atopic disease at 3, 9, and 18 months of age, but not significantly so at 6 months. At 3 months children in whom atopic disease developed later during the observation period had significantly higher numbers of blood eosinophils than children without atopy (p < 0.01). Thus pronounced eosinophilia (> 7 x 10(8) cells/L) at that age was associated with moderate or severe allergic disease during the 18-month observation period. These children continued to have eosinophilia throughout the follow-up period. Blood eosinophilia at 3 months of age also correlated significantly to cord blood IgE levels and to skin prick test reactivity later during the follow-up period. Nasal eosinophilia was a common finding and therefore had little diagnostic or predictive value.
CONCLUSIONS: Elevated eosinophil counts in peripheral blood of apparently healthy infants at 3 months of age is associated with a subsequent diagnosis of atopic disease.