erysipelas, acute infection of the skin characterized by a sharply demarcated, shiny red swelling, accompanied by high fever and a feeling of general illness. The causative agent is the hemolytic streptococcus, which often enters the body through a break in the skin. Erysipelas affects the skin of the face so frequently that when it strikes other parts of the body, it may often be misdiagnosed. Bacteremia (blood poisoning) and pneumonia are the most common complications. Erysipelas is a highly contagious disease that was formerly dangerous to life; however, it can now be quickly controlled by antibiotic therapy.