What is the definition of Erythema Nodosum?

Erythema nodosum is an inflammatory disorder. It involves tender, red bumps (nodules) under the skin.

What are the causes for Erythema Nodosum?

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:

• Streptococcus (most common)
• Cat scratch disease
• Chlamydia
• Coccidioidomycosis
• Hepatitis B
• Histoplasmosis
• Leptospirosis
• Mononucleosis (EBV)
• Mycobacteria
• Mycoplasma
• Psittacosis
• Syphilis
• Tuberculosis
• Tularemia
• Yersinia

Erythema nodosum may occur with sensitivity to certain medicines, including:

• Antibiotics, including amoxicillin and other penicillins
• Sulfonamides
• Sulfones
• Birth control pills
• Progestin

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.

What are the symptoms for Erythema Nodosum?

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:

• Fever
• General ill feeling (malaise)
• Joint aches
• Skin redness, inflammation, or irritation
• Swelling of the leg or other affected area

What are the current treatments for Erythema Nodosum?

The underlying infection, drug, or disease should be identified and treated.

Treatment may include:

• Nonsteroidal anti-inflammatory drugs (NSAIDs).
• Stronger anti-inflammatory medicines called corticosteroids, taken by mouth or given as a shot.
• Potassium iodide (SSKI) solution, most often given as drops added to orange juice.
• Other oral medicines that work on the body's immune system.
• Pain medicines (analgesics).
• Rest.
• Raising the sore area (elevation).
• Hot or cold compresses to help reduce discomfort.

What is the outlook (prognosis) for Erythema Nodosum?

Erythema nodosum is uncomfortable, but not dangerous in most cases.

Symptoms most often go away within about 6 weeks, but may return.

When should I contact a medical professional for Erythema Nodosum?

Call your provider if you develop symptoms of erythema nodosum.

REFERENCES

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.