[Rice pollen asthma and pollinosis in childhood: seasonal asthma and allergic rhinoconjunctivitis during the period of rice pollen emission in the surrouding area of rice field].

Although in 1969, rice pollen was first reported as a cause of asthma, rice pollen allergy has not been studied after the first report and thus the allergic significance of rice pollen is not well recognized at present. We investigated the sensitization to various allergens and the residential areas in children with the symptoms of asthma or rhinoconjunctivitis during the first decade of August, and measured rice pollen-specific IgE antibodies. Eighty-eight children (57 boys and 31 girls, mean age 8.5+/-2.9 years) with bronchial asthma or allergic rhinitis/conjunctivitis were included in this study and divided into two groups: children with (n=21) or without (n=67) symptoms during this period. The positivity rate to orchard grass pollen and the rate of residence in the surrounding area of rice field were high (81%, P=0.008 and 86%, P<0.001, respectively) in children with allergic symptoms, as compared to the values (48% and 27%, respectively) in children without symptoms. As the rice pollen season in Nagano occurs in the first decade of August, we measured rice pollen-specific IgE antibodies in 8 patients with symptoms during this period; all of these patients showed positive IgE antibodies to rice pollen. The RAST-inhibition assay using orchard grass and rice pollen indicated cross-allergenecity between these two pollen and also the existence of rice pollen-specific allergens. These results suggest that rice pollen induces seasonal asthma and allergic rhinoconjunctivitis during the first decade of August, which is the rice pollen season, in the surrounding area of rice fields.