Gangrene is the death of body tissue caused by a loss of blood supply, a severe bacterial infection, or both. It most commonly affects the extremities, particularly the fingers, toes, and limbs, but it can also develop in muscles and internal organs. Without treatment, gangrene spreads rapidly and can become fatal. The mortality rate for gas gangrene, the most aggressive form, approaches 100% when treatment is delayed.
How Gangrene Develops
Every cell in your body needs a constant supply of oxygen-rich blood to survive. When that supply gets cut off, cells begin to die. This is the core mechanism behind gangrene: tissue starved of oxygen breaks down and decays. The cause of that oxygen loss varies. A crushing injury, a blood clot, a severely narrowed artery, or a deep wound can all trigger the process.
Bacteria often accelerate the damage. In infected wounds, certain bacteria thrive in low-oxygen environments and produce toxins that destroy surrounding tissue. One particularly dangerous species produces at least 17 different toxins. Some of these dissolve cell membranes, killing red blood cells, muscle cells, and platelets. Others break down connective tissue like collagen, allowing the infection to spread rapidly through layers of muscle and fat. One toxin even suppresses the body’s normal immune response, which is why gangrene sometimes progresses with surprisingly little visible inflammation.
Types of Gangrene
Dry Gangrene
Dry gangrene develops slowly when blood flow to an area gradually decreases, usually over weeks or months. The tissue dries out, shrivels, and turns dark brown or black. The affected skin feels hard, cold, and numb. Because no bacterial infection is involved initially, dry gangrene doesn’t usually produce a foul smell or discharge. It’s most common in people with diabetes or peripheral artery disease and typically affects the toes and feet. While it progresses slowly, it can become wet gangrene if bacteria invade the dead tissue.
Wet Gangrene
Wet gangrene involves bacterial infection alongside tissue death. The affected area swells, blisters, and produces a foul-smelling discharge. Unlike dry gangrene, wet gangrene spreads quickly and can trigger a life-threatening body-wide infection (sepsis) within hours to days. It often follows burns, frostbite, or deep wounds that become contaminated.
Gas Gangrene
Gas gangrene is the most dangerous form. It’s caused by bacteria that produce gas as they consume dead and dying muscle tissue. You can sometimes feel a crackling sensation under the skin (called crepitus) where gas bubbles have formed. The skin may start pale, then shift to gray or purplish-red as the infection advances. Gas gangrene causes sudden, severe pain that seems out of proportion to the wound’s appearance, followed by numbness as nerves die. It spreads extraordinarily fast and carries a mortality rate of about 25% even with aggressive treatment. An outbreak among injection drug users in the United Kingdom and Ireland around 2000 saw a mortality rate of 97%.
Fournier’s Gangrene
Fournier’s gangrene is a rare, life-threatening form that specifically targets the genitals and the surrounding area (the perineum). Bacteria penetrate the deepest layer of skin and the tissue covering the muscles, spreading quickly through this space. Early symptoms include skin discoloration, swelling, and tenderness in the genital region. It progresses so rapidly that there is often no time for diagnostic tests before emergency surgery is needed.
Warning Signs and Skin Changes
Gangrene causes a characteristic progression of skin color changes. The skin first looks paler than usual due to reduced blood flow. It then turns red or reddish before shifting to brown, and finally to purple or greenish-black as the tissue dies. Other warning signs include:
- Pain followed by numbness: sudden, severe pain in the affected area that gives way to a complete loss of feeling
- Skin temperature changes: the area feels cool or cold to the touch
- Swelling and blisters: especially in wet gangrene, fluid-filled blisters may form on the skin
- Foul-smelling discharge: a sign of bacterial infection in the dead tissue
- Fever and general illness: once infection spreads, you may develop a rapid heart rate, low blood pressure, and confusion
The speed of these changes matters. Dry gangrene progresses over days to weeks. Gas gangrene can go from a small wound to a limb-threatening emergency in hours.
Who Is Most at Risk
Diabetes is one of the strongest risk factors for gangrene. High blood sugar damages blood vessels over time, reducing circulation to the extremities. People with diabetes are also at higher risk for peripheral artery disease, a condition where fatty deposits build up inside artery walls, narrowing them and further restricting blood flow to the legs and feet. When blood flow drops low enough, even a minor cut or blister on the foot can spiral into gangrene because the tissue lacks the oxygen and immune cells it needs to heal and fight off bacteria.
Other conditions that raise your risk include severe atherosclerosis (even without diabetes), Raynaud’s disease, immune system disorders, and any condition requiring long-term immunosuppressive medication. Smoking significantly narrows blood vessels and compounds the risk. Traumatic injuries, especially crush injuries or deep puncture wounds, create the oxygen-poor environment where gangrene-causing bacteria thrive. Surgical wounds that become infected are another common entry point.
How Gangrene Is Diagnosed
Doctors often recognize gangrene by its appearance, but imaging and lab tests help determine how far the damage extends. X-rays, CT scans, and MRIs can reveal gas pockets in the tissue (a hallmark of gas gangrene), show which muscles and organs are affected, and map the blood supply to the area. Fluid from skin blisters or tissue samples can be tested under a microscope to identify the specific bacteria involved and confirm cell death. Ultrasound is particularly useful for Fournier’s gangrene, where it can detect air trapped in soft tissues and help rule out other conditions with similar symptoms. In some cases, exploratory surgery is necessary simply to see how much tissue the infection has reached.
Treatment and What to Expect
Gangrene treatment has one overriding goal: remove all dead and infected tissue before the damage spreads further. This surgical removal, called debridement, is the cornerstone of treatment for every type of gangrene. In mild cases, a surgeon removes only the visibly dead tissue. In severe or rapidly advancing cases, amputation of a finger, toe, or limb may be the only way to save your life.
For infected gangrene, high-dose intravenous antibiotics are given alongside surgery to fight the bacteria. The timing of surgery matters enormously. Clinical evidence shows that initial conservative surgery paired with rapid follow-up treatment produces the best survival outcomes, while delaying intervention significantly increases both the likelihood of death and the extent of tissue loss.
Hyperbaric oxygen therapy is sometimes used as an additional treatment, particularly for gas gangrene. You sit in a pressurized chamber and breathe pure oxygen, which floods your tissues with far more oxygen than normal breathing delivers. This directly inhibits the growth of anaerobic bacteria (the kind that thrive without oxygen) and helps healthy tissue at the wound’s edges survive. It’s typically started early and may be scheduled before or between surgical procedures.
Recovery depends heavily on how much tissue was lost. Small debridements may heal over weeks with wound care. Amputations require rehabilitation, prosthetic fitting, and months of adjustment. Skin grafts are sometimes needed to cover large areas of removed tissue.
Preventing Gangrene if You’re at Risk
If you have diabetes or peripheral artery disease, your feet are particularly vulnerable because reduced sensation means you may not feel a wound developing. The CDC recommends a daily routine: check your feet every day for cuts, redness, swelling, sores, blisters, corns, or calluses. Wash them daily in warm (not hot) water and dry them thoroughly, especially between the toes. Never go barefoot, even indoors. Wear shoes that fit well, and always wear socks to prevent friction injuries.
Trim your toenails straight across and smooth sharp edges with a nail file rather than rounding the corners, which can lead to ingrown nails and infection. Don’t try to remove corns or calluses yourself, as breaking the skin creates an entry point for bacteria. Have your feet checked at every healthcare visit and see a foot specialist at least once a year. For anyone at risk, keeping blood sugar well controlled and not smoking are two of the most effective things you can do to protect your circulation and prevent the conditions that lead to gangrene.