They're small and sweet, so they may seem harmless. But for mysterious reasons, grapes can be deadly for dogs.
Recently, vets and dog owners noted that eating grapes or raisins can cause fatal kidney failure in some dogs. (The American Society for the Prevention of Cruelty to Animals [ASPCA] first noticed the danger in 1999.) Scientists still don't know what it is about grapes that causes the reaction, but they're continuing to work on discovering the root of the problem.
Dogs that eat grapes will often vomit, usually within a few hours. They may also suffer from diarrhea, abdominal pain, lethargy and loss of appetite, and they may urinate less or not at all, due to the effects the grapes have on dogs' kidneys.
Even a small amount of the fruit can cause a serious reaction, so dogs need immediate treatment if they ingest grapes. If you know your dog has eaten grapes or raisins, and the animal has not yet thrown up, induce vomiting using hydrogen peroxide. Ask your vet about the proper procedure.
Whether or not your dog vomits, immediately take it to the vet's office, where additional treatments may include activated charcoal to absorb the toxin, IV fluid treatment and dialysis. Even with treatment, some dogs don't survive.
The adverse reaction can happen in any breed or size of dog, but vets still don't know why certain dogs seem to have no reaction at all.