As others have said, this is normal behavior. However, there is biting that is not normal behavior, so make sure to eliminate other causes. Sometimes, like you observed with the teething, they bite because it relieves pain. I had a child bite mine about 12 TIMES!!!! All over the face and his back. It was terrible. The biter had a horrible ear infection and needed tubes, so we think it was because of the pain. This child did it unprovoked, he literally crawled over to my little guy and attacked him. If the biting seems to be escalating and not related to anything you can figure out, try to see if there is a medical cause. That incident made me and the other mother feel so terrible. I think it was unusual, but just keep an eye on it. The attack happened very quickly, so I would just keep a very close eye on play while he is around other children.