Erythema nodosum is an inflammatory disorder. It involves tender, red bumps (nodules) under the skin.
In about half of cases, the exact cause of erythema nodosum is unknown.
Some cases may occur with infections. Some of the more common infections are:
Erythema nodosum may occur with sensitivity to certain medicines, including:
Sometimes, erythema nodosum may occur during pregnancy.
The condition is more common in women than it is in men.
Erythema nodosum is most common on the shins. It may also occur on other areas of the body such as buttocks, calves, ankles, thighs, and arms.
The lesions begin as flat, firm, hot, red, painful lumps that are about 1 inch (2.5 centimeters) across. Within a few days, they may become purplish in color. Over several weeks, the lumps fade to a brownish, flat patch.
Other symptoms may include:
Your doctor can diagnose this condition by looking at your skin. Tests that may be done include:
The underlying infection, drug, or disease should be identified and treated.
Treatment may include:
Erythema nodosum is uncomfortable, but not dangerous in most cases.
Symptoms most often go away within about 6 weeks, but may return.
Call your health care provider if you develop symptoms of erythema nodosum.
Ferri FF. Erythema nodosum. In: Ferri FF, ed. Ferri's Clinical Advisor 2016. Philadelphia, PA: Elsevier; 2016:486-486.
Schwartz RA, Nervi SJ. Erythema nodosum: a sign of systemic disease. Am Fam Physician. 2007;75(5):695-700. PMID: 17375516
Last reviewed on: 7/23/2015
Reviewed by: Kevin Berman, MD, PhD, Atlanta Center for Dermatologic Disease, Atlanta, GA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M.