St. Anthony's fire: One of several conditions characterized by intense inflammation of the skin, such as from erysipelas or ergotism. Erysipelas is a type of spreading hot, bright-red strep skin infection. Ergotism is an intensely painful burning sensation in the limbs and extremities caused by ergotamines from a fungus (Claviceps purpurea) that can contaminate rye and wheat. The fungus produces the ergotamines, which constrict blood vessels and cause the muscle of the uterus to contract. In excess, ergotamines are highly toxic and cause symptoms such as hallucinations, severe gastrointestinal upset, and a type of dry gangrene. Chronic ergot poisoning (ergotism) was rife during the Middle Ages due to the consumption of contaminated rye.