Pyoderma gangrenosum is a rare skin condition that causes painful ulcers. It’s usually treatable but could take some time to heal and may leave some scarring.

Pyoderma gangrenosum is not related to gangrene.

Symptoms of pyoderma gangrenosum

Pyoderma gangrenosum usually appears suddenly as either a small pimple, red bump or blood blister.

The skin then breaks down into a painful ulcer with a purple or blue edge that may ooze fluid. The ulcer can grow quickly and several may develop in the area.

When to seek medical advice

See your GP as soon as possible if you think you have pyoderma gangrenosum.

It’s a serious condition that can progress quickly, so it’s important to get it diagnosed and treated as soon as possible.

Early treatment can also help reduce the risk of scarring.

If you have one of the conditions listed below, you could also contact your care team instead of your GP.

Causes of pyoderma gangrenosum

The exact cause of pyoderma gangrenosum is not understood, but it’s thought to be a reaction to a disease or illness. However, many people have no related condition and there’s no obvious reason for it.

The skin reaction isn’t passed down to children from their parents through genes. It’s also not contagious so can’t be transferred from or to another person.

The reaction may sometimes be triggered by minor skin damage or an injury – for example, it may develop around a wound, a needle prick, a biopsy or an insect bite.

When the affected skin tissue is tested, it usually has a high concentration of neutrophils (white blood cells involved in inflammation). This means pyoderma gangrenosum may be related to overactivity of the immune system.

People at risk of pyoderma gangrenosum

People with the following health conditions are most likely to develop pyoderma gangrenosum, even if the condition is mild or well controlled:

Diagnosing pyoderma gangrenosum

There’s no specific blood test for pyoderma gangrenosum.

If your doctor thinks you might have the condition, they may ask for some tests, including:

  • taking a small sample of your skin (biopsy) to help rule out other causes of skin ulcers
  • taking a swab of the wound to check for any infection
  • blood tests to check for conditions associated with pyoderma gangrenosum

Treating pyoderma gangrenosum

Pyoderma gangrenosum often heals with relatively simple treatments. However, it may take some time and often leaves some scarring in the affected area.

Some people heal very slowly, over months or years. Others may find the condition clears up within a few weeks. In some cases, it returns after treatment.

There are a number of treatment options, but there’s no clear evidence to suggest which the best one is.

Care of the wound

Regular dressings may need to be applied to soak up any discharge and help retain the creams applied to the wound. Any severely damaged tissue should be gently removed by a doctor or nurse.

Creams, ointments or injections

Strong steroid creams or ointments are applied on and around ulcers either daily or every other day. They can help the ulcers heal quickly, particularly if the ulcers are small and diagnosed early.

Alternatively, a steroid called triamcinolone may be injected into the edge of the ulcer. In more severe cases, steroids may be injected into a vein (intravenously).

Tacrolimus ointment has also proved useful in treating pyoderma gangrenosum ulcers.

Steroid tablets

Most people with pyoderma gangrenosum need to take steroid tablets, either on their own or with antibiotics. These reduce inflammation and help the ulcers to heal.

However, the long-term use of steroids is associated with serious side effects such as bone thinning (osteoporosis), so they need to be used with caution.

Read more about the side effects of steroids.


Pyoderma gangrenosum is thought to be caused by an overactive immune system. Immunosuppressants are able to reduce pain and help the ulcers to heal.

However, immunosuppressants can have unpleasant side effects, and need to be given and monitored by a specialist.

Only take immunosuppressants if they’re prescribed to you by a doctor.