Some patients with Japanese cedar (JC) pollinosis already show pollinosis symptoms before the first day of the pollen season as determined by microscopic pollen counts.Airborne pollen allergen (Cry j 1) levels were measured by electron spin resonance radical immunoassay, a highly-sensitive method for Cry j 1 with a sensitivity 10-100-fold higher than conventional enzyme-linked immunosorbent assay. The symptom data from patients with JC pollinosis were collected from a mobile phone site, "pollen check sheet", and the onset times of the patients' symptoms were analyzed.The relationship between airborne Cry j 1 levels and the onset time of pollinosis symptoms was investigated. The symptoms of some patients began at the time airborne Cry j 1 levels fluctuated at 1 to 3 pg/m3 and symptom scores increased at the time of sudden increase in Cry j 1 levels. About 40% of patients began to show symptoms until the first day of the pollen season and the time nearly corresponds to the time of sudden increase in Cry j 1 levels.Pollinosis symptoms of some patients began at the time airborne Cry j 1 levels fluctuated at 1 to 3 pg/m3 and symptom scores increased at the time of sudden increase in Cry j 1 levels. The latter time nearly corresponds to the first day of the pollen season.