Erythema nodosum is swollen fat under the skin causing bumps and patches that look red or darker than surrounding skin. It usually goes away by itself, but it can be a sign of something serious.

You may also have flu-like symptoms, such as:

• a high temperature
• tiredness
• joint and muscle pain

If you're not sure it's erythema nodosum

Check other types of lumps.

• try ibuprofen
• rest with your feet raised on a pillow
• apply a cool wet compress, like a damp cloth

The colour of the bumps and patches usually changes and fades, like a bruise.

The bumps usually heal on their own within 3 to 8 weeks without leaving a scar. But other symptoms, such as joint pain, may last several weeks or months.

If you're in pain, a pharmacist can recommend:

• stronger painkillers
• supportive bandages or stockings

A pharmacist may also suggest you see a GP.

See a GP if:

A GP should be able to tell if you have erythema nodosum by looking at the bumps and patches.

If the GP thinks a medicine you've been taking might be causing erythema nodosum, you may be advised to stop taking it. Do not stop taking your medicines without asking a GP first.

The GP might arrange some tests if erythema nodosum:

• could be a sign of something more serious
• has not cleared within 8 weeks

Erythema nodosum can be caused by lots of things, but often the cause is not known.

Common causes include:

• Crohn's disease
• ulcerative colitis
• a reaction to some medicines
• sarcoidosis
• tuberculosis
• pneumonia
• a throat infection
• a fungal infection