Clinical aspects of Japanese cedar pollinosis

Abstract

Japanese cedar pollinosis (JCPsis) is a major national health problem in Japan. The present review provides an update on information on JCPsis based on clinical data from our research group, through the support of the Department of Health and Welfare (Japanese Government), during the period from 1988 to 1997, because this disease is infrequently documented internationally despite a large number of publications from Japan. The information on JCPsis presented here may be of use in the management of various kinds of pollinosis prevalent in other countries. The prevalence rates of JCPsis vary from district to district and also depend on the age of the subjects, the method of analysis and the year of examination in population. Yet, on an average, the incidence of JCPsis is presumed to be 10-20% in adults and 5-10% in children. The risk factors for sensitization and the onset of symptoms seem to be dependent on the amount of air-borne pollen, the age of school children, hereditary disposition, including human leukocyte antigen type and the high levels of specific IgE in childhood. Because pollen counts also vary depending on many factors, such as the type of pollen samplers used, yearly variations, the number of pollen count stations, the atmospheric temperature and solar radiation in the previous year of the season, accurate predictions of daily and seasonal pollen counts are rather difficult. Commercial crude extracts and purified allergenic substances Cry j I and II correlate well with the skin test and the radioallergosorbent test. Japanese cedar pollen has an allergenic component that is cross-reactive with Japanese cypress. In many patients, the onset of symptoms occurs on the day when the air-borne pollen count is 10/cm 2 (the Durham method) and, if severe symptoms occur due to intense exposure to pollen, the symptoms will last for a long time despite variations in the pollen count (priming effect). Eye glasses, face masks and keeping windows and doors of the house closed are useful measures for pollen avoidance. Symptom control during the season is not difficult by the continuous use of new anti-allergic drugs during the season. If medication is started 1–2 weeks prior to the onset of the season, more satisfactory results can be obtained. Specific immunotherapy can not only control symptoms, but can reduce the amount of medication and, after completion of the regimen, long- term remission without medication can be expected.