Complaints of allergic rhinitis (hayfever) are common worldwide, affecting around 17 percent of the Japanese population in spring and summer (around 20 million people). In Japan, the main tree species causing hayfever are Japanese cedar and Japanese cypress, with a combined land area of over 7 million hectares. Their pollen is dispersed between February and May and causes a range of symptoms from itchy eyes and runny noses through to severe respiratory disorders.
Click here for original story, Japanese trees synchronize allergic pollen release over immense distances
Source: Phys.org