About 60 percent of the people I know are suffering pretty badly from hay fever caused by pollen from cedar trees. In order to protect themselves they are forced to wear surgical masks (some even sport goggles) in public and take anti hay fever medicine which can make you really drowsy. According to the Times, the problem now appears to have spread to snow monkeys who are also suffering from runny eyes and sneezing fits. A huge program of planting cedars was undertaken after world war two in order to build up a supply of timber that was never harvested. According to the Times the number of hay fever suffers in Japan is at one in four but I'd say that was higher in Tokyo as the problem is exacerbated by traffic pollution. I've also heard it's a cumulative problem and foreigners I've know who've been out here awhile suddenly find themselves suffering from it.
A new trend I spotted recently was people wearing colourful surgical masks like the ones above instead of the normal plain ones. These are made by Pico.