Beware of the dangers of xylitol, an artificial sweetener, in pets. Xylitol is safe for people, but because of different metabolisms, it can be fatal for dogs and cats. A simple piece of cookie could kill an animal if the danger is unknown and not addressed immediately. Hypoglycemia may compound into liver toxicity, liver damage, and ultimately liver failure. Sugar-free chewing gum is the most common cause of dogs that present to the emergency room. However, the recent introduction of xylitol as a substitute for sugar in grocery stores has increased the potential for toxicity.