Necrotizing fasciitis is a rare and potentially serious disease that affects the deeper skin tissue. It is most often caused by the bacterium Streptococcus A and is a stage of an erysipelas that has not been properly treated, but other bacteria are often found together if tests are performed. These bacteria release toxins that attack and destroy living cells. Necrotizing fasciitis begins with pain, then the affected part quickly begins to swell and redden, then turns black. Finally, the dermis blisters and necrosis or cell death begins. At an advanced stage, large, blackish, bleeding patches invade the entire affected area. The development of necrotizing fasciitis is severe in the absence of care and must be treated immediately with antibiotics and sometimes surgical removal of the necrotic areas.