ConditionSkin, hair & nails
Erythema Nodosum
Erythema nodosum is an inflammation of the fat layer under the skin that causes tender, red, raised lumps, usually on the front of both shins. It is a reaction to something else in the body, most often a strep throat, sarcoidosis, inflammatory bowel disease, pregnancy or a medicine, though no cause is found in about a third of people. The lumps heal without scarring within 3 to 6 weeks, and treatment focuses on pain relief and the underlying trigger.
Also called: EN, nodular erythema, septal panniculitis
At a glance
- What it is
- Inflamed fat under the skin (panniculitis) causing painful red nodules.
- Where
- Front of the shins on both legs; sometimes thighs, forearms or knees.
- Who gets it
- Most often women aged 20 to 45, about 3 to 6 times more than men.
- Common triggers
- Strep infection, sarcoidosis, Crohn's or ulcerative colitis, pregnancy, birth control pills, some antibiotics.
- Duration
- Each episode lasts 3 to 6 weeks; it heals without scars.
- Treatment
- Rest, leg elevation, compression, NSAIDs, and treating the cause.
When to get help
See a doctor within a day or two
- Painful red lumps on the legs with a high fever, cough, night sweats or weight loss (possible tuberculosis or sarcoidosis)
- Lumps with bloody diarrhea, belly pain or mouth ulcers
- A single hot, spreading, very red area on one leg, which suggests cellulitis rather than erythema nodosum
- Lumps that break open, ooze or form ulcers, which point to another diagnosis
Book a routine appointment
- New tender red lumps on both shins, even if you feel otherwise well
- Lumps that keep coming back
- Lumps appearing after starting a new medicine or birth control pill
Usually safe to manage at home
- Diagnosed erythema nodosum: rest with the legs raised, compression stockings and over-the-counter pain relief
What erythema nodosum is
The name means "red nodules". It is a type of panniculitis, meaning inflammation of the fat layer beneath the skin. Specifically it affects the thin walls (septa) between fat lobules. It is thought to be a delayed immune reaction: the immune system responds to an infection, a disease or a drug, and immune deposits trigger inflammation in the fat of the lower legs.
Erythema nodosum is not contagious and is not a skin infection. It is a signal that something else may be going on, which is why doctors look for a cause.
Symptoms
- Tender lumps: 1 to 5 cm (0.5 to 2 inches) across, raised, warm and painful to touch, typically several on both shins
- Color changes: bright red or pink at first, then purple, then yellow-green, like a fading bruise over 1 to 2 weeks (sometimes called erythema contusiformis)
- No ulcers or scars: the lumps do not break open
- Flu-like symptoms: fever, tiredness and aches, often a few days before the lumps appear
- Joint pain: aching or swollen ankles and knees in more than half of people, which can last longer than the lumps
- Leg swelling around the ankles
New lumps can keep appearing for 2 to 3 weeks before the episode settles.
Causes of erythema nodosum
| Category | Examples | Clues |
|---|---|---|
| Infection | Strep throat (the most common identified cause, especially in children), tuberculosis, Yersinia, Salmonella and Campylobacter gut infections, Valley fever (coccidioidomycosis), mycoplasma | Sore throat 2 to 3 weeks earlier; diarrhea; cough or travel |
| Sarcoidosis | Löfgren syndrome: erythema nodosum, swollen lymph nodes in the chest and ankle arthritis | Ankle swelling, cough, chest X-ray changes |
| Inflammatory bowel disease | Crohn's disease and ulcerative colitis | Flares often in step with bowel symptoms |
| Hormones | Pregnancy, estrogen-containing birth control pills | Usually in the first two trimesters, or after starting the pill |
| Medicines | Sulfonamide and some penicillin antibiotics, bromides, some newer cancer drugs | Starts days to weeks after the drug |
| Other inflammatory diseases | Behçet's disease, rarely lupus | Mouth and genital ulcers, eye inflammation |
| Cancer (rare) | Lymphoma, some leukemias | Persistent fevers, night sweats, weight loss |
| No cause found | About 30 to 50% of cases | Normal tests |
Löfgren syndrome deserves special mention because it has an excellent outlook: most people recover fully within 1 to 2 years without strong treatment.
How doctors diagnose it
Erythema nodosum is usually recognized by its appearance. Tests look for the trigger:
- Throat swab and ASO blood test for a recent strep infection
- Blood tests: complete blood count, inflammation markers (ESR, CRP), liver and kidney function
- Chest X-ray for sarcoidosis or tuberculosis
- TB test: an interferon-gamma release blood test or skin test
- Stool tests if there has been diarrhea
- Pregnancy test where relevant
- Skin biopsy: a deep punch or wedge biopsy that includes fat, done only when the appearance is unusual, lumps ulcerate or last longer than expected
Conditions that can look similar
- Cellulitis: usually one-sided and spreading, with a single area of redness
- Erythema induratum: nodules on the backs of the calves that can ulcerate, linked to tuberculosis
- Superficial thrombophlebitis: tender cords along a vein
- Insect bites, bruises and vasculitis
Treatment
Erythema nodosum goes away by itself, so treatment eases symptoms while treating any cause.
- Treat the trigger: antibiotics for strep, stopping a culprit drug or birth control pill, controlling bowel disease, or treating tuberculosis.
- Rest and elevation: keep the legs raised above the heart when sitting. Standing for long periods makes the lumps more painful.
- Compression stockings or elastic bandages reduce swelling and pain.
- NSAIDs such as ibuprofen or naproxen at the label dose. Avoid them in later pregnancy and in people with active inflammatory bowel disease, stomach ulcers or kidney disease; ask a doctor first.
- Potassium iodide: a prescription option for persistent or recurrent cases.
- Steroids: a short course of oral steroids or injections into a lump can help severe cases, but only once infections such as tuberculosis are ruled out, because steroids can make them worse.
- Colchicine, hydroxychloroquine or other immune medicines are sometimes used for stubborn or recurrent disease.
Outlook
Most episodes settle in 3 to 6 weeks and leave no scars, though a brown mark may linger for a few months. Joint aches can last longer. About 1 in 3 people have recurrences, often when the trigger returns, such as another strep throat or a bowel flare. Chronic forms lasting months are uncommon.
Frequently asked questions
What is the most common cause of erythema nodosum?
In many countries, a strep throat infection is the most common identified cause, particularly in children. Sarcoidosis, inflammatory bowel disease, pregnancy, birth control pills and certain antibiotics are other frequent triggers. In about a third to a half of people no cause is found, which is called idiopathic erythema nodosum.
How long does erythema nodosum last?
Each lump lasts about 1 to 2 weeks, but new ones can keep appearing, so an episode usually lasts 3 to 6 weeks in total. Aching joints can persist for several weeks after the skin clears. Episodes linked to an ongoing trigger, such as bowel disease, may return.
Is erythema nodosum serious?
The lumps themselves are harmless and heal without scarring. What matters is the cause. Most triggers, like strep throat, pregnancy or Löfgren syndrome, are manageable, but tuberculosis, inflammatory bowel disease and rarely lymphoma need to be ruled out, so a medical check is always worthwhile.
Is erythema nodosum contagious?
No. It is an immune reaction in the fat under the skin, not an infection of the skin itself, so it cannot be passed on by touch. The underlying cause, such as strep throat or tuberculosis, may be contagious and needs its own treatment.
Can stress cause erythema nodosum?
There is no good evidence that stress alone causes erythema nodosum. It is triggered by infections, inflammatory diseases, hormones or medicines. Stress may coincide with flares of conditions like inflammatory bowel disease, which can then bring on the lumps.
What does erythema nodosum look like?
It appears as several raised, tender, red or pink lumps under the skin of both shins, usually 1 to 5 cm across. The skin over them is shiny and warm. Over 1 to 2 weeks they flatten and turn purple, then yellow-green, like a healing bruise.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Dermatology: Erythema nodosum
- DermNet: Erythema nodosum
- American Family Physician: Erythema Nodosum, A Sign of Systemic Disease
- MedlinePlus: Erythema nodosum
- NHS: Sarcoidosis