Hi, it's quite possible he could be allergic to the ACV or an ingredient in it, especially since he showed the symptoms after he had some, and this was the only new thing in his diet. Every Bully is different in what they tolerate and how sensitive they are. I know there are other members who have Bullies that are allergic to ACV. I would stop giving him the ACV and keep an eye on him to see if he improves, you could also give him a Benedryl if his symptoms don't subside. Please keep us Posted on how he's doing.