I believe I've mentioned this in a previous post. I have a boy who started biting about a year ago. I found that shadowing worked wonders since he was biting when I was busy with something or someone else. Also I started to realize that there was usually something that precipitated this. I think he felt like he was being bossed around by the older girls.
The mom suggested that I give him hot sauce or bite him back. After my shock subsided, I explained to her that I couldn't do that!lol