smelly people

Why do people on the subway smell? It is bad enough being crammed in a tight train and having to touch people because you're so close. But to have them smell is just awful and almost torture. I find myself trying to smell myself without anyone realizing what I am doing because maybe this smelly person is me? I try to sniff my underarms and then brush my chin on my shoulder to make it look like I am just trying to scratch my shoulder but can't because my hands are tied up. It usually doesn't work... So I find myself trying to get an opportunity when no one is watching to put my hands under my shirt in my armpit and then smell my hand. No matter how much you think no one is watching you, someone is ALWAYS watching. You may not notice at first, but they're there all right, watching your every move... And they watch you do whatever it is you're doing and they secretly laugh at you (believe me, I know- for I am one of these people). After all this trouble I find out that the smell is not coming from me after all (didn't think it was anyways). If someone smells, how come we don't tell them they do? If a friend had a piece of spinach stuck between their 2 front teeth, why is it we don't let them know? Maybe we're embarrassed for bringing it up and to avoid that awkward moment we just say nothing at all.... I ask myself: is it rude to tell people that they smell? Is there a polite way to tell someone that they stink to high heavens and need desperately to take a shower? They say if someone has bad breath to hint at it with offering breath mints or gum whenever possible instead of just being blunt and saying nicely 'your breath is smelly'. It would be pretty awkward to offer someone deodorant, I must admit... but I think they would get the clue.