I cross posted the below information from the Greyhoundscene forum...it probably mostly concerns those of you who have hounds who are 'counter surfers'...
"Whilst most are unlikely to give left over sweets or cakes to our racing dogs our house hold pets are a different matter . Or if they are anything like mine any food item they can reach is considered theirs to eat .
Xylitol is a sugar substitute used by many manufacturers to make sweets , cakes etc and is being sold as a sugar substitute for home baking . This substance is very dangerous to dogs , the following links give more details :