Grape and Raisin Toxicity by Frank Utchen, DVM

Can raisins and grapes really poison dogs?
The answer is an emphatic yes, and everyone who owns a dog needs to know it. In this article, I’ll describe the grape-raisin syndrome in dogs and review the basic steps in treating the most life-threatening aspect of this type of poisoning: kidney failure.  If your dog ingests grapes or raisins, it is best to contact the ASPCA Animal Poison Control Center (888-426-4435), where they have specially trained staff who provide assistance to pet owners and specific diagnostic and treatment recommendations to veterinarians. Because affected dogs could die, dog owners should stop feeding their dogs grapes, raisins, and any food containing grape extracts.   If ingestion should occur, it is recommended that you seek veterinary assistance immediately to initiate aggressive medical management. For more information on the toxicity of grapes or raisins, see the ASPCA APCC Web site (www.apcc.aspca.org ).

Recently, veterinarians have recognized this new poisoning in dogs: severe acute kidney failure following ingestion of grapes or raisins.

What causes it?
The specific poisons involved in this toxicosis have eluded identification. Fungal, pesticide, and heavy-metal causes have been ruled out at this time. Investigation continues. It appears from recent unpublished data that the toxic component is within the flesh of the grape/raisin, not the seed.

What species are affected?
There are reported cases in dogs, and sporadic reports that cats may be affected. Most cats will not readily eat grapes or raisins, and this may be the reason for the lack of data in this species.

Birds do not seem to be affected (otherwise we would have no crows feeding on vineyards!).

How much is dangerous?
The lowest recorded amounts that caused kidney failure in dogs are, for grapes: 0.3 ounces of grapes per pound of body weight, and for raisins 0.05 ounces per pound. Inmore conventional terms, this would mean a 50 lb dog could be poisoned by eating as little as 15 ounces of grapes, or 2 to 3 ounces of raisins.

However, smaller amounts could also cause problems - we really don't know exactly what the minimum dose is.

However, not every dog or cat is susceptible. Many animals can tolerate large quantities of grapes or raisins without problems, and at this time no one knows what the main risk factors are that make one animal susceptible to being poisoned.

What about Grape seed Extract or grape juice?
This appears to be safe.

Toxicity has been associated with seedless grapes, so the toxin is unlikely to be within the seeds. It is then possible that grape seed extract is safe to use—however, this has not been conclusively proven. The reason this is important to know is that grape seed extract is a powerful antioxidant that may be helpful in the treatment of arthritis and other inflammatory conditions, and some dog owners use this in their older dogs.

There is no information available about grape juice or wine. However, since the toxic agent is not known, current recommendations are to avoid giving grape juice or wine to dogs or cats.

What should I do?
If you see you dog eat grapes or raisins, the smartest thing to do is to make them vomit immediately. A tablespoon of hydrogen peroxide given by mouth will usually accomplish this within 5 or 10 minutes.  

However, if there is any chance that some grapes or raisins have not been vomited up, the safest thing to do is take your dog to your veterinarian. The appropriate treatment to minimize the risk of kidney damage is to administer large amount of IV fluids for 36 to 72 hours. 

What is the prognosis?
The prognosis in cases where kidney failure develops is guarded, at best. This is medical jargon that means, very roughly: the chances of survival are 50/50.  Prognosis is good if caught immediately after a dog has eaten the grapes or raisins.