Chocolate

• Chocolate contains theobromine, a chemical that is dangerous to dogs in large amounts. The symptoms of chocolate poisoning are vomiting, diarrhea, muscle spasms and increased urination. Activated charcoal can be used to absorb the toxins. The dog will need to be monitored by a veterinarian.
  
  

Xylitol

• Xylitol is a sugar substitute that is found in many varieties of chewing gum, mints and even toothpaste. Xylitol can be lethal to dogs even in small amounts. The symptoms of xylitol poisoning are vomiting, weakness and seizures. A vet should be consulted immediately.
  
  

Grapes and Raisins

• Grapes and raisins can cause kidney failure in dogs if they are eaten in large quantities, or eaten in small number on a regular basis.
  
  

Nuts

• Most nuts, including pecans, macadamia nuts and walnuts, are dangerous to dogs. The nuts have a high phosphorous content that can lead to bladder stones or muscular disorders.
  
  

Onions and Garlic

• Onions and garlic contain an ingredient caled thiosulphate that can cause anemia in dogs.