PLEASE READ VERY IMPORTANT...........
I got this from a posting on HOTDOGBLOG.Com.......

Warning to all dog owners
Last Friday evening, I arrived home from work, fed Chloe, our 24 Lb. dachshund, just as I normally do. Ten minutes later I walked into the den just in time to see her head inside the pocket of Katie’s friend’s purse.She had a guilty look on her face so I looked closer and saw a small package of sugar-free gum. It contained xylitol. I remembered that I had recently read that sugar-free gum can be deadly for dogs so I jumped on line and looked to see if xylitol was the ingredient. I found the first website below and it was the one. Next, I called our vet. She said to bring her in immediately.Unfortunately, it was still rush hour and it took me almost 1/2 hour to get there. Meanwhile, since this was her first case, our vet found another website to figure out the treatment. She took Chloe and said they would induce her to vomit, give her a charcoal drink to absorb the toxin (even though they don’t think it works) then they would start an iv with dextrose. The xylitol causes dogs to secrete insulin so their blood sugar drops very quickly. The second thing that happens is liver failure. If that happens, even with aggressive treatment, it can be difficult to save them. She told us she would call us. Almost two hours later, the vet called and said that contents of her stomach contained 2-3 gum wrappers and that her blood sugar had dropped from 90 to 59 in 30 minutes. She wanted us to take Chloe to another hospital that has a critical care unit operating around the clock. We picked her up and took her there. They had us call the ASPCA poison control for a case number and for a donation, their doctors would direct Chloe’s doctor on treatment. They would continue the iv, monitor her blood every other hour and then in 2 days test her liver function. She ended up with a central line in her jugular vein since the one in her leg collapsed, just as our regular vet had feared. Chloe spent almost the entire weekend in the critical care hospital. After her blood sugar was stabilized, she came home yesterday. They ran all the tests again before they released her and so far, no sign of liver damage. Had I not seen her head in the purse, she probably would have died and we wouldn’t even had known why.Three vets told me this weekend, that they were amazed that I even knew about it since they are first learning about it too.
Here is more detailed info on Snopes
http://www.snopes.com/critters/crusader/xylitol.asp
Kendra