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    3. XYLITOL

    Xyli-what? You probably have this substance in your house without even realizing it. It's a sugar alcohol used in gum and toothpaste, and as a sweetener in other products. You can even buy it in powder form for baking. It's great for people because it doesn't cause a spike in blood sugar, and has been shown to reduce cavities. However, xylitol is toxic to dogs, who could experience a dangerous crash in blood pressure if they eat it. The sweetener is also linked to seizures and liver failure in dogs. Keep your gum, toothpaste, and kitchen sweeteners of all sorts in cabinets to avoid an unsweet disaster for your pooch.