Even if you don't have a dog, you might have friends who do. This is worth passing on to them. I looked on Snopes and found it's true
http://www.snopes.com/critters/crusader/raisins.asp(Below written by a vet)
This week I had the first case in history of raisin toxicity ever seen at MedVet. My patient was a 56-pound, 5 yr old male neutered lab mix who ate half a canister of raisins sometime between 7:30 AM and 4:30 PM on Tuesday. He started with vomiting, diarrhea and shaking about 1AM on Wednesday but the owner didn't call my emergency service until 7AM.
I had heard somewhere about raisins AND grapes causing acute Renal failure but hadn't seen any formal paper on the subject. We had her bring the dog in immediately. In the meantime, I called the ER service at MedVet, and the doctor there was like me - had heard something about it, but....Anyway, we contacted the ASPCA National Animal Poison Control Center and they said to give IV fluids at 1 ½ times maintenance and watch the kidney values for the next 48-72 hours.
The dog's BUN (blood urea nitrogen level) was already at 32 (normal less than 27) and creatinine over 5 ( 1.9 is the high end of normal). Both are monitors of kidney function in the bloodstream. We placed an IV catheter and started the fluids. Rechecked the renal values at 5 PM and the BUN was over 40 and creatinine over 7 with no urine production after a liter of fluids. At that point I felt the dog was in acute renal failure and sent him on to MedVet for a urinary catheter to monitor urine output overnight as well as overnight care.
He started vomiting again overnight at MedVet and his renal values have continued to increase daily. He produced urine when given Lasix as a diuretic. He was on 3 different anti-vomiting medications and they still couldn't control his vomiting. Today his urine output decreased again, his BUN was over 120, his creatinine was at 10, and his phosphorus was very elevated. His blood pressure, which had been staying around 150, skyrocketed to 220.. He continued to vomit and the owners elected to euthanize him.
This is a very sad case - great dog, great owners who had no idea raisins could be a toxin. Please alert everyone you know who has a dog of this very serious risk. Poison control said as few as 7 raisins or grapes could be toxic. Many people I know give their dogs grapes or raisins as treats including our ex-handler's. Any exposure should give rise to immediate concern.
Laurinda Morris, DVM
Danville Veterinary Clinic
Danville , Ohio