toxic substance produced by a fungus (i.e., a member of the kingdom Fungi). Mycotoxins occur in great number and variety; their effects can include hallucinations, skin inflammation, severe liver damage, hemorrhages, abortion, convulsions, neurological disturbances, and death in livestock and humans. Aflatoxins (aflatoxin) are a complex of mycotoxins produced by species of the soil saprophyte Aspergillus. They may cause liver disease and may be carcinogenic.

Food is particularly susceptible to fungal infections at almost every stage of storage or production. Some poisonous mushrooms produce symptoms that include nausea, vomiting, and diarrhea, and certain genera produce such effects as euphoria and hallucinations, but most are not considered to be lethal. One wild mushroom, Amanita phalloides, the destroying angel, or death cup, is fatal when eaten.