What is erythema nodosum? What are the symptoms?

Erythema nodosum is a skin irritation or inflammation which is located in the fatty layer of the skin, typically underneath the skin surface. This type of inflammation is commonly located in the front of the legs, below the knees, and consists of reddish, painful and tender lumps. The lumps are between the size of a dime or a quarter, and typically resolve on their own within 3-6 weeks. However, a chronic indentation in the skin may remain where the fatty layer has been injured.

What causes erythema nodosum?

Erythema nodosum is an immune system (the body’s defense system that protects the body from foreign substances or microbes that try to enter it) reaction to a variety of causes. It may be caused by medications, including birth control pills, sulfa-related drugs or diseases, such as Crohn’s and ulcerative colitis.

Who gets erythema nodosum?

Women are 3 to 6 times more likely to get erythema nodosum than men.  The peak age is from 20 to 30 years old. 

How is Erythema Nodosum related to Crohn’s and Ulcerative Colitis?

Erythema nodosum is the most common skin abnormality seen in patients with inflammatory bowel diseases (IBD), like Crohn’s and ulcerative colitis. It can be associated with a flare-up of IBD, and usually improves as the bowel disease is treated and improves. Sometimes, for those patients who are on immunosuppressive medications (those that lessen the activity of the immune system to help heal colitis), erythema nodosum can also indicate a systemic infection (such as those with fungi).

How is erythema nodosum diagnosed and treated?

Your doctor can easily to diagnose erythema nodosum through a physical exam of the affected area.  Sometimes a biopsy of the fat layer under the skin may have to be done.

Treatment for erythema nodosum is managed by managing the underlying cause of it. If the cause is Crohn’s or ulcerative colitis, then medications that help other symptoms of Crohn’s and ulcerative colitis are used to treat erythema nodosum. If the cause is an infection, then the underlying infection has to be treated in order for the erythema nodosum to resolve. Additionally, patients may receive anti-inflammatory drugs and/or cortisone to treat the skin inflammation. Erythema nodosum is not life-threatening; it does not harm your internal organs.

If you have IBD and you think you have erythema nodosum, contact your gastroenterologist as soon as possible.

For additional information on care for IBD at Rush, visit the Inflammatory Bowel Disease Program home page.

Additional information about erythema nodosum:

• Rush University Medical Center