I think grapes are one of those things you should just avoid period. Yes, some dogs can eat them and get away with it - given everything that can be toxic to dogs, there are usually some dogs out there that can get away with eating each one. My Cey got into some avocado once that we had saved for our pet rat, right after we first got him (Cey, not the rat lol). I knew avocado was on the no-no list and I sort of freaked out - but he was fine. Will I ever let him eat avocado again, knowingly? Of course not - there are waaaaayyy too many other healthy and good treats out there for him!