Eating grapes and raisins has been linked to the occurrence of kidney failure in dogs. Take note that all types of grapes have been shown to cause adverse effects on the dog’s kidneys. While the process by which grapes and raisins cause toxicity remains unclear, there have been several theories which have been advanced, including the dog’s inability to efficiently metabolize certain substances that the fruit contains, pesticide residues or mycotoxins on the surface of the fruit, or the salicylate-like chemicals in grapes or raisins. There are also cases when the problem is due to the consumption of common food items that contain grapes, raisins, or currants, such as raisin cookies, chocolate-covered raisins, cereal with raisins, raisin bread, etc.
Fortunately, grapes and raisins stay in the stomach for some time, which means they are not rapidly digested and absorbed, making it possible to buy time for aggressive decontamination. Talk to your vet for additional details.