Xylitol is a potentially deadly sweetener commonly found in sugar-free gums or candies, toothpaste, mouthwashes, and some human medications. In humans, Xylitol has little or no effect on insulin or blood sugar levels, but in dogs Xylitol stimulates a release of insulin which can cause hypoglycemia (low blood sugar). The symptoms of hypoglycemia may include disorientation, stumbling, collapsing, seizures, and even death. In larger doses, Xylitol can cause severe liver failure that can be fatal. In a 20 pound dog, as little as one piece of gum can be toxic. If you suspect that your dog has ingested Xylitol then contact your veterinarian immediately.