I have twins, one of whom started biting at 8 months of age. It seemed to be frustration he experienced when interacting with him sister. He went thorugh phases of biting constantly for months and I spent alot of time apologising to other mothers who were horrified, but I have learned a few things:-
* Biting back doesn't do anything, it just teaches them that 'an eye for an eye' is okay. His sister started biting him back and it didn't stop him.
* Be consistent when your child bites; I say 'No biting, biting is bad, look at poor ...... she's sad' and give the bitee lots of attention while ignoring the biter.
* I find it's linked alot to his teeth, he bites more when he has teeth coming so I keep teething rings in the freezer and if he bites (or looks like he's going to) I give him something to bite on.
* All the times he could have bitten, but didn't I give him extra praise and cuddles.
* He has bitten me a couple of times and it really hurts, so be understanding of the child who has been bitten.
* You've really got to catch the biting as it happens for 'No' in a harsh voice to be effective, so when other mums march up to you at playgroup with a 'please explain', explain what you do when they bite and don't feel (too) bad about it.
My son is 23 months now and he's still biting, but less often, thank goodness!