Erythema Nodosum: Inflammatory Skin Condition Triggers and Treatment

Erythema nodosum is a form of panniculitis — an inflammation of subcutaneous fat. It causes discolored, painful nodules under the skin. There are several possible causes, but often doctors cannot find an underlying cause. The condition will go away on its own, so treatment focuses on relieving symptoms.

This article describes erythema nodosum, including its symptoms, causes, diagnosis, and treatment.

Erythema nodosum is the most common form of panniculitis. However, the condition is rare, affecting up to 5 in 100,000 people. It causes inflammation of the fat tissue in the subcutaneous layer of the skin. 

Erythema nodosum results in tender lumps or nodules beneath the skin. The nodules appear on both shins, but they can occur in other places. 

The most likely explanation is that erythema nodosum is a type of allergic reaction. There are many antigens that can cause this reaction.

Erythema nodosum is not life threatening and often resolves on its own, usually over a period of up to 8 weeks. However, it can sometimes recur. Many people make a complete recovery. In the meantime, the pain is usually manageable with nonsteroidal anti-inflammatory drugs (NSAIDs).

Erythema nodosum affects people worldwide. However, the causes can vary in different regions. 

Anyone of any age can get erythema nodosum. However, biological females are 3­–6 times more likely to develop it compared with biological males. The typical ages are between 25­–40 years. The difference in sex does not affect children until adolescence. 

The characteristic symptom of erythema nodosum is lumps under the skin. The lumps are usually about 1 inch across, but they can be larger. They are firm, raised, discolored, warm, and sensitive to the touch. The lumps may fade over several weeks. 

The nodules usually appear on the shins, but they may also occur in other places, including the arms, neck, thighs, and ankles. They affect both sides of the body. The nodules do not cause ulceration or scarring.

Other symptoms that may occur include flu-like symptoms, such as:

• cough
• headache
• joint or muscle pain present about 50% of the time
• joint swelling and morning stiffness
• low-grade fever
• malaise or lethargy
• swollen lymph nodes
• unexplained weight loss

Digestive upset, including abdominal pain, nausea, and diarrhea, can also occur.

In up to half of all cases, doctors cannot find an exact cause of erythema nodosum. This is idiopathic or primary erythema nodosum.

Less often, it can be the first sign of a systemic disease or reaction, which is secondary erythema nodosum. The most common causes include:

• inflammatory bowel disease, including Crohn’s disease and ulcerative colitis
• medications, including angiotensin-converting enzyme inhibitors, antibiotics, oral contraceptives, proton pump inhibitors, and others
• pregnancy
• sarcoidosis
• strep infection, which is the main cause in children

Other possible causes include:

• acne fulminans
• autoimmune disorders, including Behcet’s disease, rheumatoid arthritis, systemic lupus erythematosus, and others
• cancer, including leukemia, sarcoma, and lymphoma, primarily Hodgkin’s lymphoma
• immunoglobulin A nephropathy
• other bacterial, viral, or fungal infections
• parasites
• tuberculosis
• vaccines
• vasculitis, such as Takayasu arteritis, granulomatosis, and polyarteritis nodosa

Erythema nodosum is rare, and there are no definitive risk factors for developing it. However, it seems to occur more often in the presence of certain conditions. Not all people with risk factors will get erythema nodosum. 

Risk factors for erythema nodosum include:

• autoimmune disorders
• inflammatory bowel disease 
• leukemia and lymphoma 
• pregnancy
• sarcoidosis
• sensitivity to certain medications
• strep throat and other infections
• tuberculosis

Erythema nodosum is mainly a clinical diagnosis. This means doctors can usually diagnose it based on the symptoms and appearance. A biopsy of a nodule can confirm the diagnosis.

Your doctor may then order additional testing to find the underlying cause, if possible. Tests may include:

• blood tests, including a complete blood count, erythrocyte sedimentation rate, and C-reactive protein
• chest X-ray
• stool culture
• throat culture
• tuberculosis test

Erythema nodosum can be uncomfortable, but it tends to clear up on its own. It usually resolves over a period of 2­–8 weeks. Nevertheless, it can sometimes recur. Treatment focuses on relieving symptoms.

Common treatments for erythema nodosum include:

• NSAIDs, such as ibuprofen (Advil, Motrin) or naproxen (Aleve, Anaprox, Naprosyn)
• potassium iodide
• colchicine, hydroxychloroquine and dapsone for resistant or recurrent cases
• systemic steroids, such as oral prednisone (Deltasone), which doctors recommend less often for resistant cases due to their side effects

Treating any underlying cause may also help symptoms resolve. 

In addition to taking medications, you may find pain relief by:

• applying cold compresses
• avoiding activities that aggravate your pain until symptoms subside
• getting bed rest
• elevating the legs
• wearing gentle support hosiery

There are no known complications of erythema nodosum itself. The condition usually resolves on its own without scarring or other changes.

However, delaying or avoiding treatment of any identified cause may result in complications specific to that disorder. You can help minimize your risk of serious complications by following your treatment plan.

Here are some questions people ask about erythema nodosum.

Erythema nodosum is not life threatening. For many people, the disorder resolves spontaneously without complications.

The most common cause of erythema nodosum is an infection, specifically a strep infection. Estimates show that 28­–48% of cases result from an infection. However, in up to 50% of cases, there is no identifiable cause.

Stress is not a known cause of erythema nodosum. Most experts believe it is an allergic reaction to a variety of antigens — substances that can promote an immune response, causing inflammation. 

Doctors recommend avoiding heavy weight-bearing exercise until lesions resolve. You may need extended rest time, which may include missing work. 

Erythema nodosum is a condition involving inflammation of the subcutaneous fat. It results in characteristic lumps under the skin that are tender and discolored. Some of these nodules can be quite large. They usually appear on both shins.

Treatment is symptomatic because the condition will resolve on its own. With time, erythema nodosum will heal without leaving scarring or permanent discoloration.