Shouldn't be a problem unless he brings the head to play ball with. I had a dog do that once. I threw it the first time. On the second time I noticed it had eyesockets.To me, as long as he's not sick afterwards, no bloody stools, and overall pretty healthy, I wouldn't worry too much. I won't let him do it all the time though. I'll keep my eye out for anything strange in case of disease and parasites.