Things that can kill dogs Dogs are very sensitive to certain foods and substances. Some can be toxic and even fatal to them: Chocolate Grapes and raisins Onions and garlic Human medications Chemicals and poisons Cooked bones that can splinter Symptoms of poisoning: vomiting, diarrhea, weakness, seizures, or internal bleeding. Keep these hazards away from your pet and see a vet at any sign of poisoning.