Ironically enough, I'm actually allergic to tobacco. That's right, allergic to it. So I only smoke outside or in the car with the windows down.
As long as I don't inhale through the mouth or nose, and keep it out of my eyes, I'm just fine. I've been that way since I was a little kid, and eventually develop pneumonia-like symptoms after prolonged exposure. I've also noticed that pipe smoke barely has any effect on me, and I can actually inhale it without problems.