Yes, Sheila. At the current time, we know that grapes and raisins appear to cause renal failure in dogs who’ve ingested large amounts. However, we have not determined with certainty the toxic component, or the exact mechanism that causes renal failure. It is also not clear if only certain dogs are affected, or if long-term ingestions can lead to the same effects that a large one-time ingestion can. Because there are still many unknowns regarding the toxic potential of grapes and raisins, it is advisable not to give grapes or raisins to dogs in any amount.