I've posted on here before about my Bullmastiff bitch.  We've had a few issues regarding temperament since an op last year (another post). But I've noticed excitement can trigger her sometimes.  Had a friend over today who all the dogs love. Lots of excitement and my collie x springer loves to bring all his toys and play fetch. (which is'nt unusual as he's like this all the while!) but as they were charging about she suddenly changed from playing into attacking him. This then happened another three times during the visit. No harm done and to be honest collie x did'nt care was more worried about his ball.  But I've not had her do this before. Does anyone know what actually happens? Is it too much adrenaline rush? How best to prevent it apart from obvious of no excitement.  The only difference today was I wormed every body with Milbemax, not sure if this can effect behaviour?
Thank you.

Sorry, no real knowledge of the facts behind this sort of thing, but my take on it is:

the dog is allready in a highened state of arousel, this tends to make any animal (including people) more 'impulsive' and can act different than when they are calmer and thinking more 'rationally'. If you have children you will probably remeber telling them to 'calm down before it ends in tears' as they get hyped up playing with each other untill someone crosses the line and somebody gets hurt!

Having kids & dogs together, I've always had this notion in the back of my mind, so when ever any play has started to get a bit too excitable, the kids & dog(s) have been seperated, before any 'accident's' happen.
Just the same when Buster is meeting/interacting with other dogs, I always keep an eye on the level of his exciement, if he's getting too excited, he gets a momentary 'time out' to calm down a bit.

> Does anyone know what actually happens?

Gonna see what I can find out on the 'net....

i think its an adrenalin rush. one of mine sometimes starts attacking the other if im about to go through the garden gate, its the excitement of wanting to get through the gate first with mine
i just try to go through gate when shes not there

I don't know the answer to your question but our rescue terrier x gets very excited and then things can get out of hand if we are not very vigilant. He gets very excited when our other dog wants to go out the back door and into the garden and would wait in the doorway ready to grab hold of him - playing at first but our other dog then wasn't keen on going in or out with him standing in the way.

We now keep a raggy toy next to the back door mat and Cooper will attack the raggy instead when he gets over excited. Obviously we don't encourage the over excitement and do remove Coops from the doorway if we are in that room so H has free access to the door but during the summer months the door is always open and the dogs come in and out as they please and it's not always possible to be in that room with them wandering in and out at will. Having something else to focus his excitement on means that Harley can come in and out at his leisure without being pounced on every time he uses the door.

Cooper spends the majority of his life in a state of high excitement/stress but rarely goes beyond that point - on the couple of occasions when his behaviour has tipped over into something else Harley has told him off and Cooper has backed down but we do our best to avoid the excitement getting out of control. All the other methods we have ever used with previous dogs - diverting attention, removing from the situation, rewarding calm behaviour etc - haven't worked with our wee terrierist but redirecting his reaction to his excitement onto something else had helped make life easier for both dogs.

I think ML's pretty much hit the nail on the head. I think some dogs are more prone to it than others, Spud can get a bit OTT if he gets too excited when playing and I usually stop him playing for a few minuets to calm down then let him play again, where as no amount of excitement would get Ben to go over the top. I've also noticed that bitches can be more prone to it than dogs ( but that's just my own experience ) the bitches I've known to do it, seemed to do it if they felt the situation was getting out of control rather than " losing the plot " and seemed to be a way of making the other dogs stop playing and calm down, obviously this wasn't a proper aggressive attack more of a " Sit on your a##e and behave ! "

Dogs do do this quite a lot when excited, they can turn on each other and sound extremely aggressive and tackle one another, but they never make skin contact or actually hurt each other, it is excitable play/training and is built into their makeup, remember dogs are supposed to hunt and bring down prey, domestic dogs have been trained to do a variation of jobs and most domestic dogs do not use their abilities anymore, the original adrenaline rush would happen whilst hunting, so when they get that rush of excitement they will often act the same way.

What you can do is distract due to the size difference as even though there is no plan to actually hurt, weight differences can hurt other dogs. :-)