Mushroom poisoning (mushroom toxicity) occurs after the ingestion of mushrooms that contain toxins, often in the context of foraging for nontoxic, similarly appearing mushrooms. Mushrooms are the fruiting bodies of a group of higher fungi that have evolved contemporaneously with plants for millions of years. They are widely distributed throughout the world. There are thousands of species of mushrooms, but only about 100 species of mushrooms cause symptoms when eaten by humans, and only 15-20 mushroom species are potentially lethal when ingested. No simple rule exists for distinguishing edible mushrooms from poisonous mushrooms. In more than 95% of mushroom toxicity cases, poisoning occurs as a result of misidentification of the mushroom by an amateur mushroom hunter. In less than 5% of the cases, poisoning occurs after the mushroom is consumed for its mind-altering properties.