I was watching the old "Karate Kid" movie the other night, and one of the things the old sensei said, during that iconic "wax on, wax off" scene, really struck me. He kept telling the kid to breathe in through the nose, out through the mouth.
I vaguely remembered hearing that suggestion somewhere else, like yoga or a martial arts class, so I decided to give it a try. It takes some practice, but after getting into that habit so I don't have to think about it, I can definitely see good reasons to.
It's cleared my nose and sinuses, and keeping them that way at a time of year I often need a hanky. It's a weird sensation inhaling cold air through my nose, but it feels warm by the time it hits my throat and chest. What really intrigues me is, somehow I don't seem to need as much air, even if I breathe solely through my nose, as when I inhale through my mouth. Maybe I absorb more oxygen that way, I don't know, but it feels both like I'm breathing more deeply, and not having to take as big of breaths, this way. Also, I can easily wait between breaths in a way I can't by inhaling through my mouth, even while walking uphill, and singing. As a result, I feel more serene, and "taken care of."
So, for what it's worth, there you go.