Thanks for the advice everyone! I thought about clipping a teething ring or soother to his shirt but I really think he needs to be taught not to bite when he's frustrated. I will see how the next few weeks go and then re-visit the soother idea. I agree that it's a serious issue and I'm not sure if the parents really understand that. I spoke with them on Friday and outlined a plan to deal with his biting. It involves us teaching him that only food goes in his mouth and then also redirecting his hitting/biting when he gets frustrated. I gave the parents some homework and they seemed on board although mom did mention a few times that she wish his teeth would just come through already ... Which leads me to believe that she is exclusively blaming teething. I'll let you guys know how it goes though and in the meantime he is not getting out of my sight, even for a second.