As far as grapes and raisins go, no one is sure why they're harmful. It's been confirmed that even grapes grown without fertilizers or pesticides can be toxic to dogs but not to every dog, and not every time. It's also not known whether small amounts eaten over a long time period could have a cumulative effect.
What we do know is that the end result in nearly all reported cases of grape or raisin toxicity is acute kidney failure. (The term "acute" means that the condition is severe and comes on quickly.) The dog ultimately can't produce urine, which means they can't filter toxins out of their systems -- a process essential to life.
During the twelve-month period in which the effects of grapes were studied, the ASPCA Animal Poison Control Center handled 140 cases involving one or more dogs. Over a third of the dogs developed symptoms ranging from vomiting to kidney failure, and seven dogs died. The ASPCA based their study on reported cases, so naturally there may be cases where a dogs health is entirely unaffected by eating grapes. But until they know all the facts, the Society advises against feeding pets grapes or raisins in any amount.
How Many Would Poison Your Dog?
The minimum toxic dose is approximately 1 grape per pound of body weight.
15 lb dog = 12-14 grapes could be deadly
25 lb. dog = 23 grapes could be deadly
50 lb. dog = 50+ grapes could be deadly
75 lb. dog = 75 grapes could be deadly
Raisins, having lost their water content are considered more toxic at 6 raisins per kg of body weight, or 2-3 raisins per pound of body weight. Think how many raisins are in ONE small snack pack of raisins? Maybe enough to kill your dog.
15 lb. dog = 30-45 raisins could be deadly
25 lb. dog = 50-75 raisins could be deadly
50 lb. dog = 100-150 raisins could be deadly
75 lb. dog = 150-225 raisins could be deadly
What are the symptoms?
Symptoms appear 6-24 hours after the dog eats raisins or grapes (average is 12 hours). Initially, symptoms are gastro-intestinal signs, followed by kidney problems.
Vomiting is usually the primary sign, with diarrhea, depression/lethargy, anorexia, colic, dehydration and sharply decreased urine output. The course of the toxicosis is anywhere from 3 days to 3 weeks. Dogs with kidney problems have a guarded to poor prognosis.
The good news is that it is treatable, if you see any symptoms, take your dog to the vet clinic immediately!!!