There is enough xylitol in a single Skittle to kill a dog. Xylitol is a type of sugar alcohol that is used as a sweetener in many products, including candy. It is also used to make medicine and as a sugar substitute in baking. It is important to note that xylitol is toxic to dogs. It could lead to vomiting and seizures. In order to figure out if Sour Skittles have xylitol, you should look for the Xylitol Warning Label on the packaging. It is important to keep your dog away from any food or snacks that have xylitol.