Japanese Cedar Pollen Allergens in Japan.

Pollen from members of the Cupressaceae tree family is one of the most important causes of allergic disease in the world. Cryptomeria japonica (Japanese cedar) and Chamaecyparis obtusa (Japanese cypress) are Japan's most common tree species. The pollen dispersal season is mainly from February to May. The major allergens of Japanese cedar and Japanese cypress exhibit high amino acid sequence similarity due to the phylogenetic relationship between the two species. An epidemiological study has shown that the prevalence of Japanese cedar pollinosis is approximately 40%. Younger children (5 to 9 years old) showed a high prevalence of Japanese cedar pollinosis as 30% in 2019, indicating that season pollinosis is getting worse. Pharmacotherapy is the most common treatment for pollinosis induced by Japanese cedar and Japanese cypress. Patients' satisfaction with pharmacotherapy is low due to insufficient experienced effect and daytime somnolence. Unlike pharmacotherapy, allergy immunotherapy (AIT) addresses the basic immunological mechanisms of allergic disease and activates protective allergen-reactive pathways of the immune system. AIT is now recognized as the only treatment option with the potential to provide long-term post-treatment benefits and alter the natural course of the allergic disease, including Japanese cedar pollinosis.