Grapes are toxic to dogs due to the presence of tartaric acid, which can cause acute kidney failure. All forms of grapes, including fresh, dried (raisins and sultanas), and grape products, are considered dangerous for dogs.
Toxicity Mechanism
The primary reason grapes are harmful to dogs is the tartaric acid found in them. Dogs are uniquely sensitive to this compound, and while the exact mechanism of toxicity was unclear for many years, recent research points to tartaric acid as the likely culprit. This acid can build up in a dog's body, as they have a limited ability to excrete organic acids, leading to kidney failure.
Variability in Reaction
It is important to note that not all dogs react to grape ingestion in the same way. Some dogs may consume grapes without apparent complications, while others can develop severe kidney injury from even a small amount. The reasons for this variability are not fully understood, but it could be due to individual sensitivity or differing levels of tartaric acid in various grapes. There is no reliable way to predict which dogs will become ill.
Forms of Grapes and Grape Products to Avoid
All types of grapes—black, red, green, peeled, seedless, store-bought, homegrown, fresh, or old—are considered toxic. Raisins, which are dried grapes, are particularly dangerous because the toxic compounds are more concentrated. It is also crucial to avoid feeding dogs food items that may contain grapes or raisins, such as hot cross buns, raisin toast, certain cakes, tarts, puddings, mince pies, some cereals, muesli, and snack bars. Tartaric acid can also be found in other fruits like tamarind and in common food additives like "Cream of Tartar".
Other Risks
Beyond chemical toxicity, grapes can also pose a physical risk. Due to their size and shape, whole grapes can be a choking hazard, especially for smaller dogs, potentially blocking their airway.
