You might think that giving your four-legged friend all the leftovers that his heart desires will make him happier, but feeding him certain human foods can cause stomach upset, diarrhea, serious health issues — or even death.
Human Foods That Are Dangerous for Dogs and Cats

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Xylitol
Keeping chewing gum in your purse is not the best idea if you have a pup with a sweet tooth. Many sugar-free candies, sweets and mints contain xylitol, an artificial sweetener that can be deadly for dogs. When ingested, xylitol causes a sudden release of insulin in a dog's body which leads to hypoglycemia (low blood sugar). Warning signs include vomiting, lethargy and trouble with coordination. If left untreated, xylitol toxicity can be fatal.

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Chocolate, Coffee and Caffeine
Chocolate contains both caffeine and a chemical called theobromine, both of which are toxic to dogs if eaten in large-enough quantities. Your dog will probably be fine if he accidentally eats a chocolate chip cookie, but depending on his size, chowing down on dark chocolate or baker's chocolate could cause vomiting, diarrhea, rapid or irregular heartbeat, restlessness, muscle tremors, seizures or death.

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Grapes and Raisins
Think grapes and raisins are healthy low-calorie snacks or treats for your dog? Think again. Whether they're plucked from a vine or sprinkled out of a box, grapes and raisins can cause acute (sudden) kidney failure in your canine. The signs of grape toxicity include vomiting, diarrhea and lethargy.

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Avocados

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Garlic and Onions
It doesn't matter if they're minced, chopped, sliced, diced, cooked or powdered — garlic and onions contain chemicals that damage red blood cells in dogs and cats. The affected red blood cells can rupture or lose their ability to carry oxygen effectively, which could lead to life-threatening anemia. Make sure you read labels carefully, as many foods, such as meat-variety baby food, contain these dangerous ingredients. And don't even think about using garlic as a cure for fleas — it doesn't work and could be more harmful than helpful to your pet.

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Macadamia Nuts
More on Vetstreet.com:
- How to Keep Your Pet's Food Safe and Recognize When It's Not
- 26 Common Household Items Dangerous to Pets
- Protein in Pet Food: What You Need to Know and Why It Is Very Important