When I first came to Japan, I was shocked to see people wearing surgical masks in public. The first time was when I was on a train. I looked around to see if anybody was looking at the middle aged woman but spotted nothing. The only conclusion I came to was that she was a doctor - but she didn't look like a doctor and even if she was - why on earth was she wearing a surgical mask on the train?!
I soon learned that people wear masks for a few reasons...
They are sick and don't want their evil germs to infect others.
They have hay fever and don't want the evil pollen to affect them.
They are not sick but don't want to catch any evil germs from others.
They have a tooth missing and want to cover it up.
Their breath smells like a fart and want to diffuse the smell.
They have no mouth and don't want people to know that they are from Mars.
This poor chap above is being a good citizen and wants to keep his germs to himself - thus the mask.
You will also see many people wearing masks during April when the hay fever season hits. I have bad hay fever too but wear a respro mask instead.
Is this mask culture specific to Japan? I've never seen people wear masks in public back in England.