You're probably not planning to feed Fido gum anytime soon. But for avid chewers who keep packs on their desk, in their cabinets, on their nightstand, take note: Xylitol, a sweetener in sugar-free gum, is seriously dangerous to dogs.
Xylitol is an artificial sweetener that's commonly found in sugar-free gum and other low-calorie foods. Because it tastes sweet but doesn't actually contain calorie-laden sugar, it's a great way to indulge your sweet tooth without adding to your waistline. But it's this very function that makes it so dangerous for dogs: when a dog's pancreas sees xylitol in the system, it mistakes it for real sugar and unleashes a flood of insulin. That insulin causes a dangerous drop in the dog's blood-sugar levels, leading to a series of life-threatening symptoms including vomiting, weakness, staggering, lack of coordination, collapse, and seizures.
If you notice these symptoms in your dog, the first thing to do is get to a veterinarian immediately. In the interim, you can feed the dog honey to raise its blood sugar, but don't force anything. Most importantly, dog owners should keep any sugar-free gum and other xylitol-laden foods out of reach of their pets, just as they would anything that could poison them.