Grape poisoning in dogs

Jacob Schor, ND, FABNO

October 10, 2014


The traditional Mother’s Day snowstorm missed Denver last spring, the one that typically freezes the blossoms on our fruit trees.  As a result the fruit trees and vines in our inner city neighborhood have yielded bumper crops.  This writer proudly admits to pittin, and freezing nearly 30 quarts of pie cherries all picked from neighbors' trees within two blocks of home.


Our dog Poppy, a ten-year-old Golden-Labrador mix, likes the taste of fruit and knows the location of every apple tree in a mile radius .  This year she exhibited a new behavior; one that at first amused us but is actually a good reason for worry.  She likes grapes.


Walking down 22nd street the other evening, she stopped and started sniffing the air, clearly she had caught the scent of something interesting.  My first assumption was that a raccoon family had taken up residence in one of the nearby storm drains.  But no, rather than dragging me to the gutter to peer down the drain, she towed me two blocks east, nose up sniffing air, turned north and led me four houses up the alley only to bury her head among the leaves of a grape wine that cascaded over a cedar fence, munching away at something as fast as she could.  It wasgrapes, lusciously ripe Concord grapes, that she now craves.  This would be entertaining except that grapes are one of those odd foods that are poisonous to dogs.


Grape and raisin toxicity is well documented in dogs. Although the exact substance that causes the toxic reaction is not known, it is clear that even small amounts of grapes or raisins may be fatal for a dog.


Dogs of any age, breed, or gender can be affected, though curiously some dogs are not bothered by grapes at all. Grape/raisin toxicity can trigger acute kidney failure, often noticed at first as lack of urine production.

There is no explanation why some dogs are not affectedt.


A clear dose-response relationship has not been determined, but as few as 4–5 grapes were implicated in the death of an 18-lb (8.2-kg) dog, a dose that that our dear dog could consume with one inhalation.


Grape poisoning is different from xylitol poisoning. Xylitol is a sugar that is growing in popularity because it is so much sweeter to the taste than most other sugars so it can be used to produce low calorie foods that nevertheless taste very sweet.  It is used to sweeten medicines and in particular dental products because it has a beneficial effect on the types of bacteria in the mouth and upper respiratory tract, encouraging what are considered beneficial bacteria to flourish and hindering growth of pathogens.  Thus for example, chewing xylitol flavored gum is a long used treatment to prevent chronic earaches and sinus infections.


The toxic effect of xyltiol was first noticed in dogs who managed to get their paws on sugarless gum.  Xylitol is nontoxic to mammals except for dogs. It doesn’t take very much to cause a big problem. In dogs, xylitol induces marked increases in insulin production and occasionally hepatopathy. The clinical syndrome is manifested with signs consistent with profound hypoglycemia, hypokalemia, hypophosphatemia, and acute hepatic failure. Treatment relies upon administration of intravenous glucose, hepatic support, and general supportive care.   In people xylitol doesn’t cause any problems, it just tastes really good.


It takes only a little bit of xylitol to cause problems. As little as 100 mg per kg can cause hypoglycemia in a dog.  The higher the dose the dog ingests, the greater the danger.  Some brands of gum contain a gram (1000 mg) of xylitol per piece, enough to affect a ten-kilogram (20 pound) dog.



Poppy weighs in at 41 Kg, so 4 pieces of gum....



Peterson ME.Xylitol.Top Companion Anim Med. 2013 Feb;28(1):18-20. doi: 10.1053/j.tcam.2013.03.008.