I have a 4 yr old Papillon which I rescued at about 1 yr old. So I don't know his history. Since then, he has been obedience trained, has his CGC, and just missed his TDI by a sausage! (my fault, I should have fed him first!!). And we have worked at agility for several years. I pretty much gave up agility after 2 yrs because he is big dog aggressive. He is always trying to get at the other dogs, esp one he doesn't know, growling, and snapping. He breaks his stay sometimes, and then takes off to "join" the big dog class. Of course, he is off lead at this point. Big trouble, little package. The big dog owners say "here comes Cujo!" laughingly, but it's not funny to me. He's going to get hurt one day. Walking away, coming back, just never seemed to work, nor "ignore him", etc. The trainers say he will probably never get over it. That's his history. But he's been fine with people. Nervous, but not aggressive.
Well, he has started biting visitors to my home. He actually goes up to them, starts to put his head toward them, and when they start to pet him, he nails them on the hand! So I don't think it's fear biting, 'cause he initiates it. Fortunately he's so small he can't do much damage, but it's got to stop. My groomer called the other day and asked where my dog was, because she didn't know where the monster came from. He had been snapping and growling at them all day, and bitten them twice. Odd behavior for him. I even brought him to the vet same day to see if they could find anything. Nothing really. He has also jumped up and grabbed a child's arm while she walking and broken the skin. And he used to be the GOOD dog!!
I'm back to making him work for everything. Basic alpha dog stuff again. I've joined this forum hoping some trainer can give me some suggestions to try. There is one other dog in the home. See my reply on someone else's "biting' post and you'll get my other dog's history. I wonder if he's not feeding off of the other dog's behavior....
Please, any ideas would be appreciated. the articles you download don't cover this problem.