[Cedar pollinosis in Japanese schoolchildren: results from a large questionnaire-based survey]

To evaluate the prevalence and clinical characteristics of Japanese cedar (Cryptomeria japonica) pollinosis (CP) in Japanese schoolchildren.

Questionnaire made by the Study Group of Epidemiology of Allergic Diseases founded by the Japanese Ministry of Public Health and Welfare was distributed to 56,108 schoolchildren living in the suburban areas of Kyoto, Japan. The data recovered from 50,086 children (recovery rate 89.3%) was analyzed.

Overall prevalence of CP was 5.2%. The prevalence was higher in older children, and in those born in autumn and winter. Prevalence of CP in southern urban area was significantly higher (p < 0.001) than that in northern rural area, suggesting that urban environment including air pollution might increase the prevalence of CP. Among children with AD, there was statistically significant correlation between the severity of AD and the presence of CP (p = 0.016), i.e. those with CP tended to have more severe AD symptoms. On the other hand, the severity of BA was not affected by the presence of CP (p = 0.323). These data suggest a contribution of cedar pollen to AD, but not to BA, symptoms. Overall, our present data shown that CP has become one of the important allergic diseases in childhood, and that further evaluation of CP among children would be necessary.