Don't know what it is about grapes. Only know the vet told me on no account to give them to my last Cocker,Deefer, who adored them He would have one 3 times a day whenever he had his eye drops. She told me she had previously given them to her dogs but had read that they were dangerous for dogs. My lovely Deefer developed stomach cancer at 8 and died within 3 weeks ,which I still cry about cos I loved him so much. Typing this is upsetting me even now nearly 3 years later. He also loved apples and apple cores and again the vet said these were toxic for dogs as the pips contain arsenic! Naturally I blamed my self for Deefer's early death . Our Cockers are so precious as are all dogs and I certainly make sure that Smudge doesn't have either of these fruits but he does love carrots so thats a good thing!