Mushroom poisoning refers to symptoms that can vary from slight gastrointestinal discomfort to death resulting from ingestion of toxic substances present in a mushroom.
The toxins present are metabolic byproducts produced by the fungus.
Typically, mushroom poisoning is the result of an eater of wild mushrooms mistakenly identifying a toxic mushroom as a non-toxic or edible species.
Because some edible and poisonous fungi have very similar appearances, mistakes are usually the result of misidentification based on superficial characteristics.
Even very experienced wild mushroom gatherers are sometimes poisoned by eating toxic species, despite being well aware of the risks.