Hmmm. do you think he's teathing? maybe he needs something to bite on throughout the day to get rid of the urge.? or is it anger? Hide around the corner and wait for him to bite....right before he does it shout "NO!" loudly, maybe that will scare him out of it? he needs to know its wrong, alot of times at that age, a booming voice will set them straight. I only had a biter once but it was temp care for a week, so I really didnt have to deal with it. GOOD LUCK!