Rhianon, I think they all bite at some stage, it doesn't make them a bully. I think it is a normal part of teething and learning about the new feeling in their mouth as new teeth come through. I personally would not bite back at all - it seems to me that teaching that something is wrong by doing the same thing is not logical or effective. What I have done is to say "no" firmly, and explain that it is not ok to bite people and that it hurts and make people sad. When he bites another child I recommend removing him from the situation into a time out. It usually is a short phase that passes once the tooth is through, and while it might happen again with another new tooth it most likely won't happen more than once or twice, and usually not for more than a couple of days at a time. If it does become more prolonged, maybe give the child health line a call for some advice.