Some dangerous dog poisons include xylitol, acetaminophen and antifreeze or other products that contain ethylene glycol, as well as several popular human foods, such as grapes. Dogs have different biochemistry from humans, so some items that, when ingested, present no issues to humans are actually very toxic to dogs.
Dogs are very prone to becoming poisoned by xylitol, a sugarless sweetener that is often found in candy, drinks, medicine and some other products, including peanut butter. Xylitol is innocuous to humans but in dogs, it causes a sudden surge in insulin. This creates a condition called hypoglycemia. This can result in coma or death. It is considered especially dangerous as it tastes enticing to dogs, can cause poisoning at small doses and many pet owners are not aware of its toxicity.
Ethylene glycol, a component of antifreeze, some windshield wiper fluids and some motor oils, is another potent dog poison. Like xylitol, it tastes enticing to dogs and cause toxicity at low doses. It causes the body to become excessively acidic. In dogs, this acidity can cause internal lesions and bleeding in the stomach and gastrointestinal tract. The chemical also causes kidney failure.
Acetaminophen, more commonly known as Tylenol, is also poisonous to dogs. It can cause liver damage. At high doses, it causes methemoglobemia, or abnormal destruction of red blood cells.
Grapes, either fresh or dried, are another common dog poison. As of 2015, scientists are not sure what makes grapes poisonous to dogs, but they can cause kidney failure. Unlike the other poisons listed above, some dogs can consume grapes without harm.