Ergotism is an acute or chronic intoxication resulting from the ingestion of grain infected with ergot fungus or from the chronic use of drugs containing ergot; characterized by vomiting, colic, convulsions, paresthesias, psychotic behavior, and occasionally ischemic gangrene (inadequate blood supply [circulation] to a local area due to blockage of the blood vessels to the area). Ergot is a fungus developed on rye plants.