Grapes and raisins can cause acute kidney failure in dogs (see also grape and raisin toxicity in dogs). The exact mechanism is unknown, nor is there any means to determine the susceptibility of an individual dog. While as little as one raisin can be toxic to a susceptible dog, some other dogs have eaten as much as a pound of grapes or raisins at a time without ill effects. The affected dog usually vomits a few hours after consumption and begins showing signs of kidney failure three to five days later. A mycotoxin is suspected to be involved, but one has not been found in grapes or raisins ingested by affected dogs. The reason some dogs develop kidney failure following ingestion of grapes and raisins is not known. The most common pathological finding is proximal renal tubular necrosis.