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Erythema Nodosum

Medically reviewed by Last updated on Feb 4, 2024.

What is erythema nodosum (EN)?

EN is a type of inflammatory disease. EN causes tender, red bumps to form under your skin. The bumps may be hot to the touch. EN develops when the fat layer under your skin becomes inflamed. You may also see bruising. The bumps are most common on your thighs, knees, shins, ankles, or feet. The bumps may be light red at first, but then they darken and may look purple or brown. You may be tired or feel like you have the flu. You may have a fever, swollen lymph glands, or joint pain.

What increases my risk for EN?

The exact cause may not be known. EN may be triggered by infections, such as strep throat, mono, hepatitis B, or tuberculosis. EN may also develop in reaction to medicines such as aspirin, antibiotics, or birth control pills. Inflammatory bowel disease, pregnancy, leukemia, sarcoidosis, and rheumatic fever have also been linked to EN.

How is EN diagnosed?

Your healthcare provider will examine you. He or she can usually diagnose this condition by looking at your bumps. You may need any of the following:

How is EN treated?

The tenderness usually lasts about 2 weeks. The red, lumpy areas usually go away on their own in 6 to 8 weeks. It is not common to have scars or open wounds with EN. Treatment may depend on what is causing your EN. For example, if you have a strep infection, you may be given antibiotics. Your medicine may be changed if it is causing your symptoms. You may also need any of the following:

How can I manage my symptoms?

When should I contact my healthcare provider?

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.