Grape and Raisin Toxicity

Updated November 10, 2025

Beginning in the 1990s, veterinarians began seeing dogs who developed acute kidney failure after eating grapes, raisins, or currants. The cause was a total mystery for decades. But in 2021, tartaric acid (the basis of cream of tartar) was discovered to be the part of grapes that cause them to be toxic to pets. The amount of tartaric acid can vary in grapes by their type, how they were grown, and how ripe they are, which could explain why some pets get very sick while others seem unaffected after eating similar amounts of grapes or raisins. Most of the tartaric acid is in the fruit and skin of the grape. There is still a lot of research and work still to do, but here’s more on this new hypothesis.

While chronic kidney disease (CKD) is commonly seen in older cats and dogs, it is usually due to a chronic, low-grade, inflammatory process called glomerulonephritis. Recent research suggests that, in cats, contributing factors may include consumption of fish, and the vaccine for panleukopenia (feline distemper). (Click here for more info on CKD in cats.) In contrast, dogs who developed grape/raisin toxicity were found to have damage and even necrosis (tissue death) in the proximal renal tubular epithelium, which is a different location in the kidney. Grape/raisin toxicity causes signs of illness within hours, and kidney failure develops within days; as opposed to the gradual development of chronic kidney disease over many months or years.Signs of acute grape/raisin/currant toxicity include vomiting, diarrhea, lethargy, loss of appetite, increased drinking and urination, and dehydration. Grape/raisin/currant toxicity has been documented only in dogs, although there have been anecdotal reports of a similar problem in cats and ferrets.

Readers have asked about the issue of grape/raisin toxicity in dogs, and what it means for the Sauvignon grape seed oil in the Omega-3 supplement MOXXOR. After thoroughly researching this issue, we have concluded that:

Tartaric acid appears to be the toxic factor, but levels in grapes vary greatly depending on variety, growing conditions, and processing factors.
The toxic reaction appears to occur in only individuals with a particular susceptibility. However, whether that susceptibility is genetic or otherwise is yet unknown.
The tartaric acid in grapes is primarily, if not entirely, in the fruit and skin.
Wine grapes like sauvignon contain seeds, but the table grapes we buy at the grocery store are seedless. The grapes dogs are usually eat are seedless varieties. It is these seedless grapes that are associated with the toxic reaction.
According to veterinary toxicology experts, there have been no reports of toxicity with the use of grape seeds, grape seed extract or grape seed oil.
The toxic dose of raisins is about 1/2 ounce of raisins, or 1/2 cup of fresh grapes (about 16 grapes) per 10 lb. of the dog’s body weight. One grape weighs about 3 grams.
The grapeseed oil used in MOXXOR comprises about 1 mg (1/1000th of a gram) per capsule.