Hi. I have a 5 year old jack Russell cross that has severe anxiety aggression issues. It doesn't seem to stem from any thing in particular and I am at a loss as to what else to do for her. She will be fine, then her whole body starts to vibrate at which point she will spin to grab her tail, however if you are in the path you will be bitten. She used to bite out at anyone around but now focusses on her tail. We have young children around and are always on the watch to make sure she doesn't bite - if she has a particularly rough day we keep a muzzle on her which calms her down. Any suggestions would be appreciated as I am at a loss on how to help her.