I just sneezed twice. Being the polite sort, even when there are only cats around (and not wanting to snot all over my keyboard and monitor) I put my hand up in front of my nose and mouth. For no particular reason, I put the back of my hand toward my face.
And on the second sneeze, I bit my own hand.
Wait, it gets better. I didn't take a hunk out of my hand or anything. My head rocked from the force of the sneeze and I caught a bit of skin on the back of my hand between an upper and a lower tooth, and the sneeze forced my jaw shut.
I now have a toothmark and a tiny, painful bruise welling up.
That's not something just ANYONE can manage, you know.