Originally thought to be an urban legend, it is now known that raisins and grapes are indeed toxic to dogs. The type of grape and the type of dog doesn't seem to matter. What's more, the toxic amount may be a small serving to several ounces.
Some dogs naturally love eating raisins and grapes and will seek them out -- whether stored in the pantry or growing in a vineyard. Pet owners have even used raisins as a training treat, and some have used them as a "healthy" snack alternative for their dogs.
Toxicity of Grapes
A computerized animal toxicity database helped veterinarians see a trend in 1989, noticing that in some cases of acute renal failure (sudden kidney failure) dogs shared a common history: the consumption of raisins or grapes just prior to the kidney failure.
Case report: Raisin toxicity in a Labrador
The type of grape or raisin doesn't seem to matter, and the amount consumed may be a single serving of raisins or a pound or more of grapes. (Raisins are much more concentrated.) Researchers are exploring the possibilities: a mycotoxin (fungal toxin), pesticide, herbicide or heavy metals, but thus far the actual toxin is unknown.
Vomiting and jittery (hyperactive) behavior are seen immediately to within the first 24 hours after ingestion. Diarrhea may also be seen, and the vomit and feces may contain partially digested grapes or raisins. After 24 hours, the dog may become anorexic, lethargic and depressed.
Additionally, the abdomen may be painful, and the dog may stop drinking and urinating. Ultimately, the kidneys fail and without aggressive treatment, many dogs will die.
If the raisin or grape ingestion was within 2 hours or less, the veterinarian will induce vomiting to rid the body of the toxin and then administer activated charcoal to absorb any remaining toxin.
Aggressive intravenous (IV) fluid therapy is required to keep the kidneys in good health. Additional kidney medications may be indicated, depending on the patient. If you suspect that your pet has consumed any amount of grapes or raisins, contact your veterinarian immediately.
Please note: this article has been provided for informational purposes only. If your pet is showing any signs of illness, please consult a veterinarian as quickly as possible.