Trends and Prospects of Japanese Cedar Pollen and Japanese Cypress Pollen Dispersal in Otsu City, Shiga

Japanese cedar pollinosis (JCP) is one of the most common diseases in Japan. The prevalence of JCP in Japan was 38.8% in 2019, and approximately 70% of patients with JCP also have Japanese cypress pollinosis. Avoiding exposure to pollen is important for managing the symptoms of pollinosis. We examined Japanese cedar pollen and Japanese cypress pollen dispersals from 1995 to 2023 in Otsu City, Shiga, Japan. Large amounts of pollen dispersal were observed every other year. High average temperatures and long hours of sunshine in the month of July of the previous year were associated with a large amount of pollen dispersal. Cedar pollen dispersal began in early February and ended in the middle of April, while cypress pollen dispersal began in late March and ended in early May. The duration of cedar pollen dispersal was longer than that of cypress pollen dispersal. The amount of pollen dispersal is affected by many factors, including the climate and the age of trees in Japan.