A toxin is a poisonous substance produced by living things like bacteria, plants, or animals. Unlike chemicals made in factories, toxins come from nature, created by organisms as they grow or defend themselves.

Some toxins protect creatures from predators. Poison dart frogs produce toxins in their skin that sicken animals trying to eat them. Rattlesnakes inject toxins through their fangs to paralyze prey. Other toxins come from bacteria: the bacteria that cause tetanus release a toxin that attacks your nerves.

Plants produce toxins too. Poison ivy creates a toxin that makes your skin itch and blister if you touch it. Some mushrooms contain deadly toxins that make them extremely dangerous to eat.

Your body works hard to filter out toxins. Your liver and kidneys act like cleaning stations, removing harmful substances from your blood. When doctors talk about food poisoning, they usually mean toxins made by bacteria growing in spoiled food.

Scientists have learned to use some toxins as medicine. Botox, used by doctors to treat certain medical conditions, comes from one of the most powerful toxins known, but in tiny, controlled amounts it can be helpful rather than harmful.