I heard a medical specialist of allergies talking about pollen allergy in Japan. He said that the cherry blossoms could be the real cause of the high percentage of "kafunsho" in Japan. The Japanese blame it on sugi (Japanese cedars), but there are few sugi in Tokyo and a lot of sakura (cherry trees). This specialist thought about this after finding that many Japanese living in England, France, Belgium and Germany also had strong "kafunsho". There is no sugi in Europe. He said that the Japanese who have kafunsho in Europe all live in residential districts with a lot of cherry trees. I think it makes sense.