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. The remaining cases are associated with an infection or other systemic disorder.
Some of the more common infections associated with the disorder are:
Erythema nodosum may occur with sensitivity to certain medicines, including:
Sometimes, erythema nodosum may occur during pregnancy.
Other disorders linked to this condition include leukemia, lymphoma, sarcoidosis, rheumatic fever, Bechet disease, and ulcerative colitis.
The condition is more common in women than it is in men.
Erythema nodosum is most common on the front of 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:
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 provider if you develop symptoms of erythema nodosum.
Forrestel A, Rosenbach M. Erythema nodosum. In: Lebwohl MG, Heymann WR, Berth-Jones J, Coulson IH, eds. Treatment of Skin Disease: Comprehensive Therapeutic Strategies. 4th ed. Philadelphia, PA: Elsevier; 2018:chap 75.
Gehris RP. Dermatology. In: Zitelli BJ, McIntire SC, Nowalk AJ, eds. Zitelli and Davis' Atlas of Pediatric Diagnosis. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 8.
James WD, Elston DM, Treat JR, Rosenbach MA. Diseases of the subcutaneous fat. In: James WD, Elston DM, Treat JR, Rosenbach MA, Neuhaus IM, eds. Andrews' Diseases of the Skin: Clinical Dermatology. 13th ed. Philadelphia, PA: Elsevier; 2020:chap 23.