Dogs should not eat grapes because grapes and raisins have been linked to canine kidney failure. Not all dogs develop kidney failure after eating grapes, but there is no way to tell which dogs are affected.
A dog with grape toxicosis typically develops symptoms within 12 hours of eating grapes. Symptoms of this condition include diarrhea, lethargy and vomiting. As the condition worsens, the sick dog may refuse to eat or drink, increasing the risk of dehydration. Death occurs within three or four days if the dog goes into kidney failure and does not recover. If the dog survives, long-term kidney problems are likely.