perhaps it is a self fulfilling prophesy. You see them sniff, you see the need to clean, they see you clean and they see the need to sniff

"My car windows are not dirty. That is my dogs nose art."

Perhaps needs more attention! Pls. check this out : [hillspet.com]

I never noticed my dog swiping his nose on anything. It's not that he doesn't, it's just that I never noticed it. I keep a reasonably clean house, but I'm not a germaphobe, and and hardly ever get sick. Dogs process their world through smells, much as we humans might read a newspaper or go online to see who's been there. If my dog wants to swipe his nose, I say let him! He lives here, too.