Many wear mask to avoid pollen in Spring
Some statistics shows that more than 30% of all Japanese are allergic to some kind of pollen. The most common allergen is cedar pollen. Due to massive plantation of cedar for the post-war recovery lumber demand, there are so many cedar trees in Japan that produces huge amount of pollen. Since avoiding to inhale pollen is the best prevention medicine, people start wearing masks in late February. In other words, masks represent start of the pollen floating season. I personally am very allergic to pollen, I have to wear masks, take medicine, injection, wear security-goggle like glasses...etc. Spring is the worst season for me!