Abstract The introduction outlines the author's methodological approach. In a departure from the historiographical tradition, she aims to demonstrate that the term Saint Anthony's Fire, coined in the Middle Ages, was only rarely used at the time to describe ergotism – a disease triggered by the consumption of a parasitic fungus on grain cereals, which mainly caused gangrene in the limbs. Adopting appropriate epistemological criteria, the author collects and interprets the different meanings of the expression in medical, literary, hagiographical and legal texts. Differing methodological approaches are needed for these sources, particularly because the disease could sometimes assume a symbolic value in non-medical texts. This requires interpretation and complicates the task of the historian studying the diseases of the past.

Keywords: diseases; St Anthony's Fire; ergotism; morbus regius; retrospective diagnosis

The ingestion of flour thus contaminated provokes real epidemics of ergotism (from ergot, the word that designates the mushroom in English and in French). Two varieties of this morbid condition are known. The first, recorded mainly in western Europe, causes very serious forms of gangrene; in the Middle Ages it was known as ‘Saint Anthony's fire’. The second, chiefly spread in central and northern Europe, provoked convulsions, extremely violent cramps, states similar to epilepsy, with a loss of consciousness lasting six to eight hours. Both forms, the gangrenous and convulsive, were very frequent due to the diffusion on the European continent of a grain-like rye, which is much hardier than wheat. In the course of the seventeenth century they often had lethal consequences, especially before their cause was discovered to be the claviceps purpurea.

The most remarkable of these epidemics, and the most serious in this period, [the early Middle Ages] was the so-called holy fire (or Saint Anthony's fire).