I was doing some reading about xylitol the other day as I am still not sure if I want to use it or not. Anyway one thing that was stress was that it is especially toxic to pets. Apparently when non-primate species consume anything with xylitol, the xylitol is rapidly absorbed into their bloodstream, causing a potent release of insulin from the pancreas. This occurs really quick; within 10-60min.
Depending on the brand of gum as little as two pieces of xylitol gum has caused severe hypoglycemia and 10 pieces resulted in liver failure.
If you have pets around the house and use xylitol you may find this link helpful.