1. Onions and garlic (Both onions and garlic contain the toxic ingredient Thiosulphate. But onions are more of a danger. Many dog biscuits contain *small* amounts of garlic – garlic contains less of this toxin so huge amounts would need to be consumed to be toxic. And, by the way, this poison builds up the system – it can be toxic in one large dose – or with repeated consumption of small amounts.)
2. Chocolate (Chocolate contains Theobromine, a compound that is a cardiac stimulant and a diuretic. This can be fatal to dogs.)
3. Grapes (Grapes are dangerous because of an unknown substance which is toxic to dogs – affects canine’s kidneys)
4. Raisins (See "Grapes" above.)
5. Most Fruit Pits and Seeds (Contain Cyanogenic Glycosides resulting in cyanide poisoning – though the fruit itself is OK.)
6. Macadamia Nuts (Macadamia nuts contain an unknown substance that is toxic to dogs.)
7. Bones (Most bones should *not* be given (especially chicken bones) because they can splinter and cause laceration of the digestive system and/or become lodged in your pet’s throat – so they also pose a choking hazard.)
8. Potato Peelings and Green Potatoes (Contain Oxalates, which can affect the digestive, nervous, and urinary systems.)
9. Rhubarb leaves (See "Potato Peelings and Green Potatoes" above.)
10. Broccoli (Broccoli is only toxic in large quantities.)
11. Green parts of Tomatoes or Green Potatoes (Contain oxalates, which can affect the digestive, nervous, and urinary systems.)
12. Yeast Dough (Yeast Dough can produce gas and swell in your pet’s stomach – leading to rupture of the digestive system)
13. Coffee, Coffee Grounds, Tea, Soft Drinks (Coffee, tea, & most soft drinks are dangerous due to the caffeine.)
14. Beer/Wine/Alcohol of any kind (Alcohol of any kind could lead to coma or even death.)
15. Human Vitamins (Human vitamins, especially those containing iron, can cause damage to the lining of the digestive system as well as cause kidney and liver damage)
16. Moldy or Spoiled Food (I think this goes without saying.)
17. Persimmons (Persimmons can cause intestinal blockage)
18. Raw Eggs and Raw Fish (Raw eggs and some raw fish can cause Salmonella poisoning.)
19. Salt, Baking Soda, Baking Powder (In large amounts these can cause an electrolyte imbalance – and severe electrolyte imbalances can lead to muscle spasm or even congestive heart failure.)
20. Mushrooms (Mushrooms may contain toxins which could cause liver and kidney damage)
21. Sugar-Substitute Containing Foods (Sugar-substitute foods containing Xylitol have been found to cause liver failure in some dogs.)
22. Nutmeg (Nutmeg can cause tremors, seizures, and central nervous system damage.)
23. Excessive Fatty Foods (Excess fatty foods can cause Pancreatitis.)
24. Avocado (All parts of the avocado and avocado tree are toxic to dogs.)
25. Diary Products (Dairy products don’t usually pose a great danger; but many dairy product have high fat content (see number 23) – and many pets are lactose intolerant – some pets more than others. Lactose intolerance leads to gas and diarrhea; though small amounts of yogurt and cheese are usually fairly well tolerated.)
http://www.animalpetsandfriends.com/Article/25-Human-Foods-Toxic-To-Dogs/300Another food that you should never give your dog even though they are made and heavily marketed for dogs is Rawhide Bones as they can cause intestinal blockage or be a choking hazard that is far to common. These damn things should be illegal. Similar chew treats that aren't dangerous are pig ears or other various commercially prepared and preserved hooves or bones.
http://www.petplanet.ca/education_articles/nutrition_rawhide.htmlWhy is Rawhide Dangerous?
* Rawhide can swell up to four times its original size in your dog’s stomach causing life threatening blockages.
* Dogs can and will chew off and swallow large pieces of rawhide which can get stuck in their esophagus, stomach or intestines. This almost always requires surgical removal.
* Rawhide is not considered a food item, and is therefore not covered by any labeling, processing or content laws.
* Rawhide contains chemical preservatives and has been treated with other chemicals in processing.
* Salmonella bacteria are often present especially if the rawhide comes from outside North America.
* Arsenic, ethoxyquin, formaldehyde and other chemicals such as BHA and BHT are commonly used as preservatives.
* Other dangerous additives can include antibiotics, lead and insecticides. Some countries may even include pieces of dog and cat skin in these products.
* Rawhide chews can cause acute pancreatitis, which can vary from mild gastrointestinal upset to collapse and death