Apples, peaches, and cherries can contain small amounts of cyanide, which is toxic to dogs. citrus fruits contain citric acid, limonin and oils. These have been linked to irritation and possible even central nervous system depression dogs. of couse,, a single wedge of orange may only give your dog a stomach-ache.
Grapes and raisins can cause canine kidney failure.
Garlic and onions can cause unusual changes in a dog's red blood cells
Other harmful foods include avocadoes, coffee and tea, macadamian nuts, Bologna and other processed lunchmeats etc.