st. anthony's fire st. anthony's fire st. anthony's fire (also known historically as ignis sacer and holy fire) may refer to: ergotism, the effect of long-term ergot poisoning, traditionally due to the ingestion of alkaloids erysipelas, an acute infection, typically with a skin rash st anthony's fire (novel), a 1994 doctor who novel by mark gatiss shingles, a painful viral disease, also called herpes zoster