Ergotism
Ergotism is the effect of long-term ergot poisoning, classically due to the ingestion of the alkaloids produced by the Claviceps purpurea fungus which infects rye and other cereals, and more recently by the action of a number of ergoline-based drugs. It is also known as ergotoxicosis, ergot poisoning and St Anthony's fire.  In Italy and in Malta, shingles is also known as St. Anthony's fire.

# Causes
The toxic ergoline derivatives are found in ergot-based drugs (such as methylergometrine, ergotamine or, previously, ergotoxine).  The deleterious side-effects occur either under high dose or when moderate doses interact with potentiators such as azithromycin.
Classically, eating grain products contaminated with the fungus Claviceps purpurea also caused ergotism.
Finally, the alkaloids can also pass through lactation from mother to child, causing ergotism in infants.

# Symptoms
The symptoms can be roughly divided into convulsive symptoms and gangrenous symptoms.

## Convulsive symptoms
Convulsive symptoms include painful seizures and spasms, diarrhea, paresthesias, itching,  headaches, nausea and vomiting. Usually the gastrointestinal effects precede central nervous system effects. As well as seizures there can be hallucinations resembling those produced by LSD (lysergic acid diethylamide), and mental effects including mania or psychosis. The convulsive symptoms are caused by clavine alkaloids.

## Gangrenous symptoms
The dry gangrene is a result of vasoconstriction induced by the ergotamine-ergocristine alkaloids of the fungus. It affects the more poorly vascularized distal structures, such as the fingers and toes. Symptoms include desquamation, weak peripheral pulse, loss of peripheral sensation, edema and ultimately the death and loss of affected tissues.

# History
Epidemics of the disease were identified throughout history, though the references in classical writers are inconclusive. Rye, the main vector for transmitting ergotism, was not grown much around the Mediterranean. When Fuchs 1834 separated references to ergotism from erysipelas and other afflictions he found the earliest reference to ergotism in the Annales Xantenses for the year 857: "a Great plague of swollen blisters consumed the people by a loathsome rot, so that their limbs were loosened and fell off before death."
In the Middle Ages the gangrenous poisoning was known as ignis sacer ("holy fire") or "Saint Anthony's fire", named after monks of the Order of St. Anthony who were particularly successful at treating this ailment. The 12th century chronicler Geoffroy du Breuil of Vigeois recorded the mysterious outbreaks in the Limousin region of France, where the gangrenous form of ergotism was associated with the local Saint Martial as much as Saint Anthony.
The blight, named from the cock's spur it forms on grasses, was identified and named by Denis Dodart who reported the relation between ergotized rye and bread poisoning in a letter to the French Royal Academy of Sciences in 1676 (John Ray mentioning ergot for the first time in English the next year), but "ergotism" in this modern sense was first recorded in 1853.
Research by Linda Caporael (1976) suggests that many of the people whose accusations resulted in the 1692 Salem witch trials in Massachusetts were genuinely suffering hallucinations and other symptoms of convulsive ergotism.
Similar eruptions of ergotism also occurred in Essex and Fairfield counties in Connecticut that damp and cool season, though in Connecticut no one went to the gallows. Notable epidemics of ergotism, at first seen as a punishment from God, occurred up into the 19th century. Fewer outbreaks have occurred since then, because in developed countries rye is carefully monitored.
When milled the ergot is reduced to a red powder, obvious in lighter grasses but easy to miss in dark rye flour. In less wealthy countries ergotism still occurs: there was an outbreak in Ethiopia in mid-2001 from contaminated barley. Whenever there is a combination of moist weather, cool temperatures, delayed harvest in lowland crops and rye consumption an outbreak is possible. Russia has been particularly afflicted.
Poisonings due to consumption of seeds treated with mercury compounds are sometimes misidentified as ergotism, such as the case of mass-poisoning in the French village Pont-Saint-Esprit in 1951: The incident is described in John Grant Fuller's book The Day of St Anthony's Fire.