What Is Erythema Nodosum? Causes, Treatment, and Images
Key takeaways:
Erythema nodosum (EN) is a lumpy, tender rash. It typically affects the front of your shins, but can occur in other areas of your body.
In most cases, an exact cause for EN is never found. But it may also be related to a more serious underlying condition.
EN often heals on its own without any treatment, but medications like nonsteroidal anti-inflammatory drugs (NSAIDs) and steroids can help relieve your symptoms.
Erythema nodosum (EN) is a rash that causes tender, reddish-purple lumps, especially on the shins. EN can happen to anybody, but it’s most common in women in their 20s to 40s. Often, no specific cause of EN is ever found, and it typically heals on its own. But sometimes, EN can be related to an underlying health condition.
Let’s take a closer look at what erythema nodosum looks like (with pictures), and discuss its causes, symptoms, diagnosis, and treatment.
What does erythema nodosum look like?
Erythema nodosum causes tender, warm, reddish-purple lumps about 1 inch to 2 inches wide. In people with darker skin tones, the skin might appear darker in the tender spot, or there may be no color change at all.
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EN lumps are smooth — they don’t open up or ooze. They usually occur on the shins, but other areas may be involved, including the forearms, legs, and buttocks.
EN takes a couple of days to pop up, and the lumps go away within 2 months. As they heal, the color changes from red-purple to yellow-brown-blue-green (like a bruise). Sometimes, skin darkening can continue for months after EN heals.
Pictures of erythema nodosum
Here are some pictures of erythema nodosum on different skin tones.
What are other symptoms of erythema nodosum?
Some people may also experience flu-like symptoms 1 to 3 weeks before developing the rash. These symptoms might include:
Fever
Fatigue
Joint pain
What causes erythema nodosum?
Scientists are not 100% sure what causes erythema nodosum. In many cases, EN is idiopathic, which is another way of saying that it “happens for no clear reason.” More often than not, a specific cause of EN is never identified.
Still, EN has multiple known causes. Examples include:
Infection: When a cause is identified, infection is the most common one. Bacterial infections (like strep throat and tuberculosis), and fungal and viral infections can all cause EN.
Medications: Common culprits include penicillin, birth control pills, and sulfa drugs.
Pregnancy: Some people may develop EN during pregnancy.
Cancer: Any type of cancer might cause EN, but Hodgkin lymphoma, leukemia, and carcinomas are the most common types that cause it.
Autoimmune conditions: Autoimmune conditions, like sarcoidosis and Crohn’s disease, may also cause EN.
Is erythema nodosum an autoimmune condition?
Not exactly. EN is a rash caused by an immune system overreaction to some kind of trigger. But it’s not a disease in and of itself. Think of it more like an immune symptom.
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How is erythema nodosum diagnosed?
Healthcare professionals can often diagnose erythema nodosum just by looking at it — especially when it shows up on your shins. If EN is located in an unusual area, a skin biopsy might be necessary. This involves removing a small piece of skin and looking at it under the microscope.
What should be done to look for a cause of erythema nodosum?
Usually, no specific cause for erythema nodosum is found. But since EN can be associated with more serious conditions, a healthcare professional will ask you questions and order additional tests to check for them if needed.
When thinking about causes of erythema nodosum, a healthcare professional will ask about:
Recent medication use: Remember to mention any over-the-counter (OTC) medications and herbal supplements you may be taking, too.
Recent travel and activities: Travel to certain places or certain outdoor activities might raise the risk of some infections.
Any other symptoms: Mention anything you may have noticed out of the ordinary in the past few weeks. These symptoms could be clues to help determine the cause of your condition.
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After a thorough conversation, you’ll have a thorough physical exam. Additional tests might be ordered, too. Examples include:
Blood tests to look for signs of infection or inflammation
Stool tests, if stomach symptoms like diarrhea or abdominal pain are present
Pregnancy tests, if there’s a chance you might be pregnant
Throat swabs to check for strep throat (if you have symptoms)
Chest X-rays, which can check for sarcoidosis, tuberculosis, or other lung infections
What are the options for erythema nodosum treatment?
Erythema nodosum commonly goes away on its own after a few weeks, so treatment is often not needed. To relieve your symptoms while your EN heals, consider the following:
Resting
Propping up your legs
Gentle compression with bandage wraps or compression socks
Medications may speed up the healing process and lessen symptoms. If treatment is needed, first-choice medications are nonsteroidal anti-inflammatory drugs (NSAIDs), like ibuprofen and naproxen. These medications are available over the counter or with a prescription.
However, NSAIDs are not a good option for people with kidney disease, stomach ulcers, or heart disease. They are also not recommended after 20 weeks of pregnancy.
If NSAIDs aren’t an option or your symptoms are very severe, let a healthcare professional know. Stronger anti-inflammatory medications called “steroids” — like prednisone — can sometimes help treat your symptoms.
Erythema nodosum skin changes rarely become chronic or recur. In these cases, other medications can spare your body from repeated use of NSAIDs and steroids. Examples include:
Steroid injections
How serious is erythema nodosum?
Erythema nodosum is uncomfortable and may be inconvenient. But fortunately, it’s not life-threatening or a serious condition.
Frequently asked questions
So far, there aren’t any studies looking at whether certain foods can cause erythema nodosum. It’s best to stick to a whole-foods diet with a variety of vegetables and fruits, and avoid ultra-processed foods as much as possible. Avoiding foods that have been linked to inflammation may help reduce the risk of underlying conditions that lead to EN, but there isn’t much evidence to support that.
Stress doesn’t seem to be a direct cause of erythema nodosum. But, stress may contribute to some other underlying causes of EN. For example, stress can weaken your immune system and make you more likely to get an infection.
The symptoms of erythema nodosum are usually pretty characteristic. But sometimes, it can look like some other rashes, including:
The bottom line
Erythema nodosum (EN) is a tender, lumpy rash triggered by an immune response to something. In most cases, that “something” is never found, and EN just gets better on its own. Sometimes, EN is a symptom of a more serious condition. A healthcare professional will ask you questions and examine you to determine if more tests are needed. Treatment might be nothing at all or a short course of anti-inflammatory medications.
Why trust our experts?
Images used with permission from VisualDx (www.visualdx.com).
References
Bolognia, J., et al. (2017). Skin biopsies: What you should expect. Yale Medicine.
DermNet. (2019). Erythema nodosum.
Markman, M. (2022). Carcinoma. City of Hope.
Mert, A. (2007). Erythema nodosum: An evaluation of 100 cases. Clinical and Experimental Rheumatology.
Oakley, A. (2021). Necrobiosis lipoidica. DermNet.
Pérez-Garza, D. M., et al. (). Erythema Nodosum: A practical approach and diagnostic algorithm. American Journal of Clinical Dermatology.
Requena, L., et al. (2002). Erythema nodosum. Dermatology Online Journal.
U.S. Food and Drug Administration. (2022). FDA recommends avoiding use of NSAIDs in pregnancy at 20 weeks or later because they can result in low amniotic fluid.
