Erysipelas is a superficial bacterial skin infection caused by group A beta hemolytic streptococci, that characteristically extends into the cutaneous lymphatics. The inciting event is the bacterial inoculation into an area of skin trauma An interdigital fungal infection of the foot may provide a nidus for infection for instance. Face, arms, and legs are the most frequent anatomic location. Erysipelas typically begins as a small erythematous patch that rapidly progresses to a fiery-red, indurated, tense, and shiny plaque. The characteristic appearance suggests the diagnosis and it can be differentiated from cellulitis by its characteristically raised advancing edges and sharply demarcated borders (owing to its more superficial nature). With treatment, the lesion often desquamates and resolves with pigmentary changes.
Ref: Bisno AL, Stevens DL: Streptococcal infections of skin and soft tissues. N Engl J Med 1996 Jan 25; 334(4): 240-5