Raisins and grapes are toxic to dogs. The actual toxic component hasn't been identified, but the ASPCA has been tracking cases of animal poisoning since 1989 and has found that most dogs developed kidney failure after eating these fruits. (Animal Watch; Dr. Means)
The Animal Poison Control Center keeps a computerized database, AnTox, to track such cases. They noted that most of the dogs would produce partially digested grapes and raisins in vomit or feces within a few hours.
Toxic Dose:
Their studies show that dogs that ingested as few as 10 to 12 grapes for a 20-pound dog showed signs of toxicity. Raisins are 4.5 times as toxic as grapes, so even a small amount can produce symptoms. (Petplace.com)
Symptoms:
All of the dogs started vomiting within six hours; some would stop eating and develop diarrhea. Some were quiet and lethargic; some showed signs of abdominal pain. Symptoms could last for several days or weeks.
Blood tests results:
Blood chemistry panels showed elevated blood calcium, and elevated blood urea nitrogen, creatinine and phosphorous - signs of kidney failure. Those signs increased from 24 hours to several days after the fruit's ingestion. As kidney damage progressed, the dogs could not produce urine and death occurred. Some animals had to be euthanized. (APCC, Means)
Even in cases where the fruits were grown without pesticides, fertilizers or antifungals, the results were the same.
Treatment:
Any dog suspected of having eaten grapes or raisins should be seen by a vet immediately. First, someone should induce vomiting and give activated charcoal to help prevent further absorption of toxins.
The dog should be hospitalized for aggressive treatment. They will usually be placed on IV fluids for at least 48 hours and watched for signs of kidney failure. If everything appears normal after three days, the dog will probably be OK. If the kidneys begin to fail, other medications will be used to stimulate urine production.
Today, because of valuable data from this database, increased public awareness, and quick intervention and treatment by vets, many dogs can be saved and completely recover from a toxic overdose of grapes or raisins.
Grapes and raisins are not treats; they are poison to dogs. Be informed. Be alert. And get your dog to a vet ASAP if you see signs of toxicity.