The cold and flu seasons and the allergy seasons are the times when you see the most mask wearing. This picture is from the former, but what the heck.
Before coming to Tokyo, I never had any allergies. I credit this partially to good genetics, but also to having grown up in a rural area with clean air. Living in a city with pollution tends to eventually cause some people to develop allergies. It can't be helped, but it still is annoying that repeated exposure to dirty air sends ones histamine response into overdrive. The thing which annoys me more is the fact that allergy medication which is equivalent to the type you can buy over the counter back in the United States costs a fortune here, and can only be purchased via prescription and cannot be paid for with the Japanese health insurance card.
I won't miss the fact that it costs about $1.50 per pill for (the same) medication (Claritan) that I can pay about $10 per bottle of 100 tablets for back home.