Poisoning often depends on the amount of the substance and the individual, however.
Aspirin, safe in small doses for most people, kills more children each year through overdoses than the poisons everyone recognizes as dangerous. Even small amounts of aspirin can effectively poison a person who is allergic to it or who has certain blood disorders. Blood toxins, such as carbon monoxide, act on the blood cells to deprive the body of life-giving oxygen. Many organic poisons, such as snake venom or fungal poisons, are in this class. Corrosive poisons, such as ammonia, lye, and sulfuric acid, attack and destroy bodily tissues directly.