Killer in the rye: St. Anthony's fire

Signs of St. Anthony’s fire were easy to see: seizures, hallucinations, and blackened limbs. Medieval Europeans believed its cause to be spiritual, but the true cause was far more earthly.

Peter Bruegel the Elder painted "The Beggars" in 1568. The figures in this detail may depict survivors of St. Anthony's fire. Oil on wood, Louvre Museum, Paris
Photograph by Bridgeman/ACI

The 17th-century French historian, François Eudes de Mézeray, chronicled a plague that swept through southern France in the 10th century: “The afflicted thronged to the churches and invoked the saints. The cries of those in pain and the shedding of burned-up limbs alike excited pity; the stench of rotten flesh was unbearable.” Throughout the Middle Ages, many outbreaks occurred, some taking tens of thousands of lives. Symptoms included convulsions, hallucinations, and excruciating burning sensations in the limbs. Dubbed ignis sacer, holy fire, the affliction blackened the limbs until they fell off at the joint.

Common wisdom of the time held that the sickness was spiritual and that divine intervention could treat it. Special hospitals were set up, manned by monks of St. Anthony of Egypt, famous for his spiritual strength in the face of torment from the devil. The terrible condition was then associated with the saint, and became known as St. Anthony’s fire. (See also: The science behind the Plague.)

In the 18th and 19th centuries science revealed that the condition is caused by eating grain infected with a fungus, Claviceps purpurea. Infected plants bear black growths resembling a rooster’s spurs (ergot in French), giving the condition its modern name: ergotism.

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