contagious infection of the skin and underlying tissue, caused by group A B-hemolytic streptococcus bacteria. Erysipelas causes affected areas of skin to turn bright red and become slightly swollen. The swollen blotches have a distinct border and slowly expand into the surrounding skin. The lesions are most commonly seen on the face, scalp, hands, and legs. They feel hot to the touch and the patient is feverish.

Centuries ago erysipelas epidemics caused severe and often fatal infections. In AD 1089 one of the most severe epidemics was known as St. Anthony's fire because those who prayed to St. Anthony were said to recover; others, who did not, died. Today erysipelas is a rather mild and relatively rare infection that clears up rapidly when penicillin or other antibiotics are taken. Even without treatment the infection usually disappears in several weeks, but treatment is necessary to ensure against such potential complications as nephritis, subcutaneous abscesses, and blood poisoning (septicemia) from bacterial toxins. Antibiotic treatment also ensures against a recurrence of the infection and its transmission to others.