Prevalence of inhaled antigen sensitization and nasal eosinophils in Japanese children under two years old

Abstract

Objective: The increasingly younger age of onset of allergic rhinitis (AR) has recently become a problem. This study examined the prevalence of inhaled antigen sensitization and nasal eosinophils in children younger than two years old, with measurement of the serum concentrations of aeroallergen-specific IgE antibodies to house dust mites, cat fur, and Japanese cedar pollen, measurement of nasal eosinophil counts, and a questionnaire administered to the children's parents.

Methods: The subjects were a group of healthy children undergoing 18-month infant health checks provided by the local government, and sick children younger than two years old at the pediatric hospital.

Results: Among 408 healthy infants, 44 (10.7%) had antigen-specific IgE antibodies, 29 (7.1%) had nasal eosinophils, and eight (2.0%) had both specific IgE antibodies and nasal eosinophils. Nasal assessment revealed that 125 children had rhinorrhea. Of the infants who showed both sensitization to antigens and nasal eosinophils, six (1.5%) had confirmed rhinorrhea. Among 186 sick children younger than two years old at the pediatric hospital, aeroallergen-specific IgE antibodies were detected in five (2.6%). The presence of nasal eosinophils was confirmed in six children (3.2%), which percentage was smaller than that of the healthy group. No infant had either sensitization to antigens or nasal eosinophils.

Conclusion: The findings described above indicate that the minimum prevalence of AR might be 1.5% in 18-month-old children and that around 10% of affected children have aeroallergen-specific IgE antibodies in Japan. The incidence of AR in young children might increase further.