Giving your dog human food may seem like a harmless treat, but you could be putting your dog's life in grave danger. Dogs have a different physiology from us, and foods that are harmless to us may be life-threatening to dogs. Here are some common foods that can be fatal to dogs:

1. Chocolate. A wonderful treat for us humans, but a deadly poison for dogs. Chocolate has a chemical called theobromine which dogs cannot metabolize properly. It stays in a dog's body and can cause diarrhea, heart attacks, internal bleeding, and death. A small chocolate bar can be enough to kill a small dog. If your dog eats any chocolate, contact a veterinarian immediately. Also beware of chocolate found in cakes, candy, and drinks.

2. Macademia Nuts. Found in cookies, chocolates and all sorts of candy. They can cause dogs to be paralyzed or have weakness in their movement, or trembling legs. It is not known if this can kill dogs.

3. Onions, Garlic and Chives. These have the chemical thiosulphate, which can give your stomach pains, sometimes only several days after eating them. They can also cause anemia which can kill some dogs. Cooking or heating these vegetables does not remove thiosulphate, so onions, garlic and chives are dangerous whether they are raw, cooked or appear in processed food. Be careful if you feed human biscuits or canned food to your dog, they often have some of these ingredients in powder form.

4. Raisins and Grapes. Found in cookies, cakes, candy bars, and in raw form. They can cause kidney failure in some dogs a few days after consumption. Some dogs seem to be less susceptible, and other dogs more susceptible to it.

5. Avocado. It has a chemical compound called Persin which can cause damage to a dog's organs. Avocado is found in guacamole, so don't let your dog near a guacamole dip.

6. Xylitol (found in sugar free foods). Xylitol is believe to be generally safe for humans, but it can cause dogs to have low blood sugar and liver failure. This is often found in toothpaste, sugar free sweets, candy, and gum.

7. Alcohol and Tobacco. Nicotine is poisonous to dogs, who can get heart attacks or fall into a coma after eating it. Don't let your dog eat cigarette butts or any other type of tobacco. Alcohol causes dogs to get drunk, the same way as it does in humans. However dogs are much smaller, so they can easily die of alcohol poisoning from what might seem to be a small amount of alcohol.

8. Bones. Yes, believe it or not, animal bones can be dangerous for dogs. Dogs have been known to choke on bones, or swallow sharp bones which puncture their digestive tract. This can be fatal.

9. Fruit Seeds and Pits. Dogs can choke on them, or get them stuck in their digestive tracts. Some seeds and pits also have trace amounts of chemicals which are safe to humans, but can cause cyanide poisoning in dogs.

The best general guideline is to avoid feeding your dog any human food. You dog may love table scraps and sweet treats, but they can be deadly. Human foods also tend to contain too much sodium (in salt) which can cause skin and health problems for dogs. They often also have too much fat for small animals like dogs. Dog food, which has been formulated specially with the dog's health in mind, is the safest and healthiest food for dogs.

Image credit: Christian Gidlöf