What is necrotising fasciitis?

Necrotising fasciitis is a rare but serious and painful infection caused by bacteria. It is also sometimes called ‘flesh-eating disease’. The lower leg is the most common place for this infection to happen.

Necrotising means killing tissue. Tissue is made of similar cells that work together to do a specific job in your body.

Fasciitis means inflammation of the fascia — the soft tissue around your muscles, nerves, fat, and blood vessels.

When bacteria infect the soft tissue, they release toxins (poisons) that cause blood clots. This cuts off the blood supply, causing your skin, muscles and tissues to die.

The infection can spread quickly in the body, causing your body to damage its own organs and tissue. This is known as sepsis. It can make your organs stop working properly.  

What are the symptoms of necrotising fasciitis?

Necrotising fasciitis can affect many parts of your body. For example, your arms, buttocks, trunk, head or neck. The most common area of infection is the lower leg. Early symptoms can quickly become severe.

Early symptoms

Look out for early symptoms, such as:

• skin that first looks normal but then quickly turns red, purple, or blue
• skin becomes swollen, shiny and warm
• extreme tenderness and pain in or around the area of a wound

Worsening of symptoms

Treat worsening symptoms promptly:

• skin begins to break down
• blisters and dead skin tissue become visible
• pain may lessen as your small blood vessels get blocked and nerves are damaged

Severe symptoms

If you or someone else is having trouble breathing, or if you have symptoms of stroke, heart attack or other signs of thrombosis, call triple zero (000) and ask for an ambulance.

The bacteria can cause a severe infection throughout your body (sepsis). It can also form blood clots in a vein or artery (thrombosis). This can cause symptoms such as:

• high temperature (fever) and chills
• low temperature
• fast heart rate
• having very little or no urine output (weeing)
• feeling exhausted, confused or sleepy
• flu-like symptoms such as nausea, diarrhoea, dizziness and a general feeling of being unwell

What causes necrotising fasciitis?

Necrotising fasciitis happens when bacteria enter the body through a break in the skin and infects the soft tissue. Group A streptococcus bacteria is one of the most common causes.

These bacteria are often found on your skin, near the anus, genitals, and in the throat, without causing harm.

Bacteria can enter your body through:

• cuts, grazes or tears in your skin
• burns
• surgical wounds
• minor wounds like a prick from a rose thorn or insect bites
• a bump or hit that does not break the skin
• skin punctures from intravenous drug use (when a needle is used to inject drugs directly into the bloodstream)

In open wounds, the bacteria grow fast and release toxins and enzymes that cause septic shock, making blood pressure drop and cause blood clots. These blood clots cut off your blood supply and can cause tissue in your skin and muscles to die.

Not everyone has streptococcus A bacteria on their skin. The bacteria can spread through skin contact with other people.

Some other uncommon types of flesh-eating diseases include those caused by M. ulcerans (buruli ulcer, sometimes called ‘Bairnsdale ulcer’) and M. leprae (leprosy) and some fungi.

You are more likely to get necrotising fasciitis if you:

• have a weakened immune system
• have diabetes, kidney disease, liver disease, a heart or lung condition or cancer
• use steroids, alcohol or drugs
• are older
• are living with obesity

It can also be a rare complication of chickenpox in young children.

When should I see my doctor?

If you experience any severe symptoms or if your symptoms worsen rapidly, call triple zero (000) for an ambulance.

You should see your doctor if you:

• have deep wounds or wounds that won't stop bleeding
• are unable to clean dirt or debris from a wound
• see any foreign objects such as thorns or glass in your wound
• have cuts over joints or gaping wounds
• have changes around your wound, such as swelling, redness or increasing pain
• have wounds from animal bites that may have been contaminated with soil or saliva
• if you have a wound and you also have diabetes

How is necrotising fasciitis diagnosed?

Getting diagnosed quickly is important to be able to treat the infection before it causes severe damage or even death.

Your doctor will look at your skin and do tests, such as:

• ultrasound — to help find necrotising fasciitis early
• CT scan — a 3D image of a part of your body, which is helpful if the diagnosis is not clear
• biopsy — your doctor might take a small piece of the infected skin for testing
• blood test — which can show if you have an infection or muscle damage
• wound cultures — to test for which bacteria is causing the infection

How is necrotising fasciitis treated?

Your doctor will try to find out which bacterium is causing the infection. It will then be treated with strong antibiotics given directly into a vein through a drip (intravenous or IV).

If the infection has caused a lot of damage and reduced blood flow, antibiotics might not be able to reach all the infected areas. Your doctor might decide that surgery is the best way to remove the damaged tissue.

You might need more than one surgery to remove the damaged tissue. You may also need a blood transfusion. Sometimes, if the infection is very severe, amputation of one or more limbs might be necessary.

It’s best to be fully prepared for any surgery. Ask your doctor if you have any questions before surgery, as this can help guide you towards making the decision that’s right for you.

Can necrotising fasciitis be prevented?

There are currently no vaccines to prevent streptococcus A infections, including necrotising fasciitis.

Good wound care is the best way to prevent bacterial skin infections. You can look after most smaller wounds yourself. Keep them clean to prevent infection. If you have wounds, avoid swimming in rivers, lakes and swimming pools where bacteria live. Treat fungal infections, because fungi may also cause necrotising fasciitis.

Complications of necrotising fasciitis

Necrotising fasciitis is a serious infection that can be life threatening. It can cause serious complications, such as:

• failure of one or more of your organs
• septic shock
• losing a limb
• bad scarring
• toxic shock
• death

Resources and support

Call healthdirect on 1800 022 222 at any time to speak to a registered nurse (known as NURSE-ON-CALL in Victoria) for more information and advice.

You can find more information about necrotising fasciitis on the DermNet website.

Visit Sepsis Australia for more information on sepsis or if you or your family or friends need support.

Visit the Department of Health website for more information on taking care of wounds.

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Health Translations has translated information on many health topics including invasive group A streptococcal disease.