There are many human foods that should not be given to dogs, but chocolate, raisins, grapes, macadamia nuts and mushrooms are among the most dangerous. Some foods that are safe for humans contain substances that are toxic to dogs.

Chocolate contains theophylline, theobromine and caffeine, all of which can cause vomiting and diarrhea in dogs. In some cases, chocolate is even toxic to the nervous system and heart. Raisins and grapes contain a toxin that damages the kidneys. Macadamia nuts also contain a toxin that harms the nervous system, digestive system and muscles. Mushrooms are very dangerous because they contain compounds that can cause shock or death.

Garlic and onions are also dangerous for dogs because they contain disulfides and sulfoxides. These compounds cause anemia by damaging the red blood cells. Although meat isn't toxic to dogs, a pet owner should never feed a dog raw meat. Doing so increases the risk the dog will be exposed to E. coli or Salmonella bacteria.

Pet owners should also avoid feeding their dogs a lot of table scraps. Even if the scraps aren't inherently dangerous, eating too much human food can throw a dog's diet out of balance. If table scraps are given as a treat, the bones should be removed and excess fat trimmed off meat.