I have only ever experianced this once with my dogs, and this was with my dog Toby.. but I was really my fault, I moved my body inbetween a dog fight, even though I know I'm not supose to. He hit on my wrist and bumped me aside at first I didn't know what to think of it until I looked into it a bit more. Other then that none of my dogs have ever done that to me, but I have seen them do that to each other from time to time.