Cats can eat a small amount of avocado flesh, but should not the skin (or the pit) as they contain persin, a substance mildly toxic to cats and dogs. Cats should not eat avocados because it is high in fat and they can upset your cat’s stomach and cause vomiting, diarrhea or obstruction of stool. Avoid giving avocado to cats with preexisting gastritis and pancreatitis conditions or you can risk the return of pancreatic inflammation for the affected cats.