From the Boston Herald on January 20, 2917
Q My 3-year-old female Weimaraner got into a large quantity of grapes at the house this morning. After some quick research, I reached for some hydrogen peroxide and gave her a few teaspoons. Within a few minutes, she vomited up three large piles of the barely chewed grapes. I took her into my vet’s office, and they ran some tests and gave her some fluids and medication. She seems well now. What could have happened to my dog if she had eaten these grapes and I was not around?
A Grape toxicity can lead to kidney failure, with typically the signs of vomiting and diarrhea occurring a few hours after ingestion. Lethargy and a loss of appetite also can be seen, along with a lack of urine production. Raisins can also be toxic. Since they are dried grapes, they are toxic in a smaller quantity. The toxic dose for grapes is about 1⁄2 ounce per pound of body weight, but that can vary, so any consumption should be taken seriously.
I often suggest that if vomiting can be induced within an hour of an ingested toxic substance, then chances are good that the toxin will not have detrimental effects on the patient. One must be cautious in using hydrogen peroxide. The actual suggested dosage to induce vomiting is 1 ml per pound, and never give a large dog more than three tablespoons.