Erythema Nodosum

What is erythema nodosum?

Erythema nodosum (EN) is a type of inflammatory disease. It causes nodules, or bumps, to form under your skin. EN is more common in women than men.


Symptoms of erythema nodosum

Nodules are the main sign of EN. They can look similar to bruises, but have firm, bumps under your skin. The nodules often are tender and painful, and can be hot to touch. They are red at first and then can turn purple or brown. Nodules are most common on the lower half of your body. This includes your thighs, knees, shins, ankles, and feet.

Other possible EN symptoms include:

  • fever
  • flu-like feeling
  • achy joints
  • swelling or inflammation
  • irritated skin.

What causes erythema nodosum?

EN can be linked to infections, such as streptococcus (strep). Other common infections include tuberculosis (TB), mononucleosis, and hepatitis B. Reactions to certain medicines, such as antibiotics or birth control pills, may trigger EN.

Other conditions that may be related to EN are:

  • leukemia
  • lymphoma
  • inflammatory bowel disease (IBD)
  • rheumatic fever
  • pregnancy.

Sometimes, the exact cause of EN is unknown.

How is erythema nodosum diagnosed?

Typically, your doctor can diagnose EN by looking at your symptoms. They may do a biopsy to confirm or order tests to determine a cause. For example, a throat culture can check for a strep infection. A chest X-ray can check for tuberculosis.

Can erythema nodosum be prevented or avoided?

You cannot prevent or avoid EN.

Erythema nodosum treatment

Treatment may depend on if something caused EN. If your doctor suspects a reaction to medicine, they may change your prescription. If you have an infection, the doctor can prescribe antibiotics or steroids.

General forms of treatment include:

  • pain medicines to relieve discomfort
  • nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce swelling
  • elevation of the affected area to reduce swelling
  • a cold or hot compress to relieve pain and reduce swelling
  • rest.

Living with erythema nodosum

Most cases of EN are not severe and go away in about 6 weeks. Talk to your doctor if it lasts longer or you get it more than once.

Questions to ask your doctor

  • What is the best form of treatment?
  • If I get EN once, what is the chance of it coming back?