Hello Peter, As Jeanne said the affliction, St Anthony's fire, is caused by the ergot fungus. I was given to understand that ergot is a form of LSD, which explains the hallucinations. it also explains why a whole community might be affected if they all eat rye bread from the same source. There is a suggestion that the apparitions seen by those who were later tried as witches could be attributed to eating affected rye bread. Cheers, Janet Heskins (Surbiton, Surrey)