Many different types of bacteria can cause this infection. A very severe and usually deadly form of necrotizing soft tissue infection is due to the bacteria Streptococcus pyogenes, which is sometimes called "flesh-eating bacteria" or strep.

Necrotizing soft tissue infection develops when the bacteria enters the body, usually through a minor cut or scrape. The bacteria begin to grow and release harmful substances (toxins) that kill tissue and affect blood flow to the area. With flesh-eating strep, the bacteria also make chemicals that block the body's ability to respond to the organism. As the tissue dies, the bacteria enters the blood and rapidly spreads throughout the body.

Symptoms may include:

• A small, red, painful lump or bump on the skin that spreads
• A very painful bruise-like area then develops and grows rapidly, sometimes in less than an hour
• The center becomes dark and dusky and then turns black and the tissue dies
• The skin may break open and ooze fluid

Other symptoms may include:

• Feeling ill
• Fever
• Sweating
• Chills
• Nausea
• Dizziness
• Weakness
• Shock

Your health care provider may be able to diagnose this condition by looking at your skin. Or, the condition may be diagnosed in an operating room by a surgeon.

Tests that may be done include:

• Ultrasound
• X-ray or CT scan
• Blood tests
• Blood culture to check for bacteria
• An incision of the skin to see if pus is present
  
• Skin tissue biopsy and culture

Treatment is needed right away to prevent death. You'll likely need to stay in the hospital. Treatment includes:

• Powerful antibiotics given through a vein (IV)
• Surgery to drain the sore and remove dead tissue
• Special medicines called donor immunoglobulins (antibodies) to help fight the infection in some cases

Other treatments may include:

• Skin grafts after the infection goes away to help your skin heal and look better
• Amputation if the disease spreads through an arm or leg
• Hundred percent oxygen at high pressure (hyperbaric oxygen therapy) for certain types of bacterial infections

How well you do depends on:

• Your overall health (especially if you have diabetes)
• How fast you were diagnosed and how quickly you received treatment
• The type of bacteria causing the infection
• How quickly the infection spreads
• How well treatment works

This disease commonly causes scarring and skin deformity.

Death can occur rapidly without proper treatment.

Complications that may result from this condition include:

• Infection that spreads throughout your body, causing a blood infection (sepsis), which can be deadly
• Scarring and disfigurement
• Loss of your ability to use an arm or leg
• Death

This disorder is severe and may be life threatening. Contact your provider right away if symptoms of infection occur around a skin injury, including:

• Drainage of pus or blood
• Fever
• Pain
• Redness
• Swelling

Always clean the skin thoroughly after a cut, scrape, or other skin injury.

Necrotizing fasciitis; Fasciitis - necrotizing; Flesh-eating bacteria; Soft tissue gangrene; Gangrene - soft tissue

Abbas M, Uçkay I, Ferry T, Hakko E, Pittet D. Severe soft-tissue infections. In: Bersten AD, Handy JM, eds. Oh's Intensive Care Manual. 8th ed. Philadelphia, PA: Elsevier; 2019:chap 72.

Fitzpatrick JE, High WA, Kyle WL. Necrotic and ulcerative skin disorders. In: Fitzpatrick JE, High WA, Kyle WL, eds. Urgent Care Dermatology: Symptom-Based Diagnosis. Philadelphia, PA: Elsevier; 2018:chap 14.

Pasternack MS, Swartz MN. Cellulitis, necrotizing fasciitis, and subcutaneous tissue infections. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 93.

Updated by: Elika Hoss, MD, Assistant Professor of Dermatology, Mayo Clinic, Scottsdale, AZ. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.