Erythema Nodosum

Who's At Risk?

Erythema nodosum can develop in people of any age, sex, and race / ethnicity. Young adults are particularly susceptible to developing erythema nodosum. Additionally, women are 4 times more likely than men to be affected.

Up to half of cases of erythema nodosum have no underlying cause. However, an associated medication, infection, or health condition may be found in the remainder of cases.

Erythema nodosum may develop in people taking medications such as:

• Birth control pills.
• Estrogen.
• Antibiotics (such as sulfonamides or penicillin).

Erythema nodosum may occur in persons with:

• Streptococcal infections (such as strep throat).
• Intestinal infections.
• Tuberculosis.
• Pneumonia (viral or bacterial).
• Fungal infections (such as coccidioidomycosis or histoplasmosis).

Erythema nodosum may be seen in individuals:

• Who are pregnant.
• Have inflammatory bowel disease (such as ulcerative colitis or Crohn disease).
• Have sarcoidosis.
• Have a malignancy, such as lymphoma or leukemia.

Signs & Symptoms

The most common locations for erythema nodosum include the:

• Shins.
• Knees, ankles, or thighs.
• Buttocks.
• Forearms.
• Face and neck.

Erythema nodosum appears as one or more warm, painful nodules (solid, raised, firm bumps) or plaques (raised or bumpy areas that are larger than a thumbnail). They usually range in size from 1-6 cm in diameter. In lighter skin colors, they are typically bright red; in darker skin colors, they are often dusky red or purplish.

Initially, there may also be fever, generalized achiness, leg swelling, or joint pain, especially in the ankles and knees.

Individual nodules of erythema nodosum usually last from 1-2 weeks, but new lesions may continue to appear for up to 6 weeks. When an individual lesion of erythema nodosum has resolved, it may leave behind what looks like a bruise, which subsequently fades to normal-appearing skin. The skin color changes can be especially long lasting in darker skin colors.

Self-Care Guidelines

The tenderness of the skin lesions may be alleviated with:

• Restriction of physical activity.
• Bed rest.
• Elevation of the legs (if they are affected).
• Cool or warm compresses.
• Acetaminophen (eg, Tylenol), ibuprofen (eg, Motrin, Advil), or aspirin (eg, Bayer).

Treatments

If diagnosed with erythema nodosum, your medical professional will attempt to identify a possible cause, such as a medication, infection, or medical condition. They may order diagnostic tests such as blood work, chest x-ray, or a throat culture. If an underlying cause is identified, the medical professional will treat it appropriately (for example, by discontinuing a medication, prescribing antibiotics for an infection, or treating a health problem).

Once those investigations and treatments are under way, your medical professional may recommend the following measures to make you more comfortable:

• Restriction of physical activity, bed rest, leg elevation, and compression of the affected area(s)
• Anti-inflammatory medications
• Potassium iodide
• Steroids (either taken in pill form or injected directly into the lesions)

Visit Urgency

Since erythema nodosum can be associated with underlying infections or health problems, a medical professional should be consulted within a few days of noticing the skin lesions.

Trusted Links

• MedlinePlus: Skin Conditions
• MedlinePlus: Skin Infections
• Clinical Information and Differential Diagnosis of Erythema Nodosum

References

Bolognia J, Schaffer JV, Cerroni L. Dermatology. 4th ed. Philadelphia, PA: Elsevier; 2018.

James WD, Elston D, Treat JR, Rosenbach MA. Andrew’s Diseases of the Skin. 13th ed. Philadelphia, PA: Elsevier; 2019.

Kang S, Amagai M, Bruckner AL, et al. Fitzpatrick’s Dermatology. 9th ed. New York, NY: McGraw-Hill Education; 2019.