Some fungi have been known to produce toxins that are harmful to animals and humans when ingested, inhaled or in contact with the skin. The fungi that produce toxins are known as toxigenic fungi. The earliest known toxigenic fungi, primarily Claviceps purpurea, produce the substance, ergot. The ergot fungi infect rye, grains and other grasses. Ingestion of ergot contaminated rye or other cereals causes ergotism.
Gangrenous ergotism affects the extremities as well as causes some gastrointestinal symptoms.
Convulsive ergotism affects the nerve system causing brain and spinaf lesions, which can lead to death or permanent mental impairment. Many fungi in addition to ergot fungi produce secondary toxic metabolites, such as alkaloids, cyclopeptides, and eoumarins. Mycotoxins are a problem to farmers and food industries and in Eastern European and third world countries. Many species in the genera Aspergillus Penicillium and Cladosporium are known to produce rnycotoxins. These three groups of fungi are also very common indoors.