Never Give These Foods to Your Pet Grapes, avocados, cookies are dangerous for dogs, cats By Matt Cantor, Newser User Posted Nov 23, 2014 1:48 PM CST Updated Nov 23, 2014 1:50 PM CST 23 comments Comments Human cookies aren't for pets. (AP Photo/Ivan Pierre Aguirre, File) (Newser) – You may have heard that you shouldn't give chocolate to your dog—but how about grapes? Or sugar-free gum? Alternet lists eight foods that humans may consume, but pets definitely shouldn't: Sugar-free treats like gum, which contain xylitol. The sugar alcohol is extracted from fruits and vegetables to be put in gum, toothpaste, sugarless baked goods, and more. If a 20-pound dog eats a couple of sticks of the gum, it can suffer hypoglycemia and even death. Chocolate, coffee, and sodas, which contain methylxanthine compounds. They can cause seizures and heart problems in pets, and a single chocolate bar can lead to death. Avocados, which carry a toxin known as persin. It's not just dangerous to cats and dogs: Birds, hamsters, and guinea pigs can experience serious health problems from the stuff, too. Cookies, which could contain macadamia nuts or other dangerous ingredients. Macadamia nuts, or macadamia powder or oil, can make dogs very sick for reasons that are unclear. Grapes and raisins, which "can lead to acute kidney failure in pets," says a vet, noting that "we didn’t know about this until a few years ago." Onions, garlic, and similar foods, which can make it harder for your pet's blood to carry oxygen. Watch out for garlic and onion powder in soups, sauces, and elsewhere. Click for Alternet's full list.