According to the latest information from the animal poison control Center, as few as seven grapes can be toxic to an adult dog. So allowing one or two grapes might be okay, but if you see your dogs eating a large number of grapes then you should call your veterinarian.
Why Grapes Are Bad for Dogs
Currently we do not know why grapes are toxic to dogs but it appears to severely affect their kidneys.
Signs of Grape Toxicity
Signs that your dog may exhibit after eating grapes include vomiting, diarrhea, lethargy, abdominal pain, and anorexia. Eventually, many dogs develop signs of renal failure.
What To Do
If you see your dog eating grapes you should call your veterinarian immediately. They may either instruct you to carefully observe the dog, to induce vomiting, or to bring your dog immediately into the clinic.
Depending on how long ago your dog has eaten the grapes your vet may induce vomiting or give provide activated charcoal to try and absorb some of the toxins.
Summary
While we may not know how many grapes are toxic to a dog or the exact mechanism, it is a bad idea to give your dog grapes or raisins. If you have small children you should instruct them to never give people food to the dog without your permission.
