Pets & Plants

An Update on the dangers of Grapes and Raisins

Various types of grapes (Vitus species) and raisins are common food items consumed by people and available to be eaten by pet animals as well. Pets are exposed to grapes and raisins in many ways. Frequently, dogs will eat grapes off the vine, steal from plates or be offered fruit as treats. Grapes and raisins have been recommended as treats and training aids because they are tasty and relatively low in calories. Unfortunately, dogs and possibly other pet animals can have serious, lifethreatening reactions to ingestion of grapes and raisins.

Adverse reactions to consumption of grapes and raisins have been well documented in dogs with anecdotal reports of problems in cats and ferrets. Affected dogs have eaten grapes and raisins purchased from grocery stores, as well as grapes found in the garden and even grape pressings from wineries–both seedless and seeded grape varieties have been implicated. The toxic component and mechanism involved with the adverse effects have not been identified previously but a new report suggests that the toxic substances may be tartaric acid and potassium bitartrate. Two dogs were reported to suffer acute kidney damage when exposed to cream of tartar (potassium bitartrate) and the lesions in their kidneys were identical to those caused by grape and raisin toxicosis. Tartrates are considered to have a wide margin of safety in people.

In dogs, grape and raisin toxicosis cause acute kidney failure, which can be a life-threatening condition if not treated early and aggressively. As few as 1 to 2 grapes per kilogram body weight (10 to 14 grapes for 20-pound dog) may cause problems. Luckily, not all dogs develop problems after consuming grapes. For raisins, consumption of greater than 3 grams per kilogram body weight is potentially toxic (¼ cup raisins for 25-pound dog).

Vomiting is one of the initial signs of grape or raisin poisoning and can begin within 3 to 6 hours after eating the offending material. Other initial signs that can occur within the first several hours of exposure include diarrhea, lethargy and excessive thirst. Signs of kidney failure (loss of appetite, lethargy, vomiting, diarrhea, abdominal pain, tremors) may develop within 24 hours or be delayed several days after exposure. Reports of vomiting and acute kidney failure have also been reported recently in dogs following large exposures to tamarind fruit, which are also uniquely high in tartaric acid. Treatment includes early decontamination (induce vomiting within a few hours of exposure) and aggressive therapy for acute kidney failure with intravenous fluids and appropriate drugs.

All cases of grape, raisin, tamarind or cream of tartar ingestion should be considered potentially serious in dogs. Do not feed grapes, raisins, tamarind fruit or products made with large levels of cream of tartar (for example, homemade play dough) to dogs for any reason and keep them away from grape plantings where they might help themselves to a tasty but dangerous treat.

PHIL ROUDEBUSH Veterinarian

Phil Roudebush is a retired veterinarian and specialist in small animal internal medicine. He was an Extension Master Gardener in Shawnee County, Kansas before moving to western North Carolina five years ago, where he is an Extension Master Gardener in Buncombe County. He can be reached at philroudebush@gmail.com.