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While most “people-foods” can be fed to Fido without any adverse consequences, some should never be fed to dogs because they pose a serious potential health risk. Here are five poisonous people-foods, and some warning signs that they may have been ingested by your dog.

Grapes & Raisins

The consumption of large amounts of grapes or raisins can potentially cause fatal kidney failure if untreated. However, some dogs seem to be more susceptible to adverse reaction and toxicity than others. Raisins are more risky than grapes because they are concentrated. An occasional grape or raisin isn’t usually problematic, but there have been reported cases of toxicity from consumption of only a handful of either one.

Signs of grape or raisin toxicity include vomiting or diarrhea (pieces of grape or raisin may be visible), shaking, abdominal pain, weakness and excessive thirst (but reduced urine output). If you suspect your dog has eaten either of these foods, veterinary care should be sought immediately.


Chocolate that is especially high in cocoa contains high levels of threobromine which can cause a severe reaction that worsens with the type of chocolate, the volume consumed and the smaller the dog. For example, it would take 20 ounces of milk chocolate to be fatal for a 20 pound Fido but only two ounces of dark chocolate.

Theobromine is like caffeine and affects the nervous, cardiovascular and peripheral nervous systems. It has a diuretic effect as well. Clinical signs of chocolate ingestion include extreme excitability and restlessness, increased heart rate and muscle tremors, gastro-intestinal upset including diarrhea and vomiting, and increased urination.

Macadamia Nuts

Ingestion of these can cause a toxic reaction called macadamia nut toxicosis. An unsteady gait, elevated temperature, depression, vomiting, muscle tremors and an increased heart rate are among the signs, and these usually subside within a couple of days but occasionally can result in severe shock, which may even be fatal. The problems are worse from consumption of chocolate covered macadamias.


The consumption of onions by Fido can lead to Heinz Body Anemia, in which damage to the red blood cells occurs, leading to their premature rupture. This is caused by a toxic substance called thiosulfate, contained in onions.

The initial signs of onion toxicosis actually appear a few days after onion consumption and include gastro-intestinal upset, diminished appetite and general weakness. As the condition advances, Fido may become breathless, as there are fewer oxygen-carrying cells in his system. Blood may also be seen in the urine.

All types of onion contain thiosulfate including raw and cooked, and those included in other foods like pizza, pasta sauce or Chinese meals. Fairly large quantities of onion have to be consumed in order for a problem to occur, although these large quantities can cause Heinz Body Anemia whether consumed in one meal (for example a bowl of chopped onion stolen from a counter-top) or in smaller quantities over a long period of time (such as frequent, repeated meals of “people-food” with onion in the recipe).

While garlic also contains the toxic ingredient thiosulfate, garlic is much less toxic and extremely large amounts would need to be eaten to cause illness.


Xylitol, a sugar substitute, is often found in chewing gum, candy, sugar-free pudding, jello, diabetic foods and toothpaste. It can be fatal to pets. Xylitol causes mass insulin release in dogs, leading to sudden hypoglycemia, a drop in blood sugar levels. Fido can show symptoms in as little as 20 minutes, or as late as 12 hours after the consumption of Xylitol.

Symptoms include ataxia (staggering gait), depression, lethargy, confusion, seizures and in some cases, death.

Lucy Postins is a monthly columnist in Fido Friendly Magazine.

Check out some other articles about pet food:
Hypoallergenic Pet Food: Myths and Facts
Pet Food Ingredients Guide
The Importance of Pigments in Foods

© 2013 Lucy Postins & The Honest Kitchen This article may only be copied with prior written permission from the company. Reproductions must include credit to the author and a link to this website.