Erythema nodosum (leprosy): what it is, causes and treatment

Who has never practiced any sport and ended up hurting the shin? This is a common occurrence, which can cause some purples on the skin that appear and disappear over time.

But what about when reddish spots and nodules appear on the shin even without you doing anything? This can be a warning sign from your body for any health-damaging condition.

It may be the case of erythema nodosum, a disease in which spots and reddened nodules appear in the shin area, and can also appear in the knees and thighs causing a lot of pain in the joints.


What is erythema nodosum?

Erythema nodosum is the name given to red and painful lumps that appear on the skin, especially in the region of the shin. In some cases it can affect the ankle, thigh, forearm and knee.

These nodules are a problem of inflammatory origin, being a type of panniculitis, that is, an inflammation of the fat layer that is under the skin.

The causes of this problem are often unknown, but among the alternatives are the manifestation of infections, allergies to some medication, the development of a more serious disease such as tuberculosis, etc.

It is known that some factors help to trigger the condition, they are: smoking, malnutrition, the presence of diabetes , HIV or cancer treatment, kidney diseases, among others.

The nodules are red and painful, and the patient may experience pain when touching it. There is also a burning sensation, a different color from one day to the next, etc.

For the diagnosis to be made, it is necessary to seek a dermatologist, who will evaluate the case and treat it in the best way. The treatment consists of the use of medication and rest, in some cases the nodules can disappear spontaneously in up to 3 months.

Erythema nodosum is a rare condition, which can be found in the International Statistical Classification of Diseases and Related Health Problems, the ICD 10 by the code L52 – Erythema nodosum.

Histopatologia do eritema nodoso

The erythema nodosum consists of a type of septal panniculitis, which is characterized by the appearance of nodules in the shin region due to the inflammation process that occurs in that region of the body.

Histologically, acute inflammation occurs at the onset of the condition, with the presence of cells such as neutrophils, eosinophils and basophils (which act on the immune system, destroying invading agents).

With the course of the erythema nodosum, lymphocytes, histocytes or giant cells (which participate in the immune system) totally or partially replace the erythematous composition. This leads to the healing of the region (fibrosis) and the permanence of inflammation, but the presence of neutrophil cells is less in relation to recent edema.

Eritema nodoso e tuberculose

When tuberculosis settles in the patient’s body it can cause erythema nodosum, which is a symptom.

Called Bazin’s indurated erythema , the nodules on the skin are caused by the same bacteria as tuberculosis ( Mycobacerium Tuberculosis ).

There is, therefore, an association, albeit infrequent, between erythema nodosum and tuberculosis. In this case, they tend to be firm and painful, in some cases they can be ulcerated on the lower limbs.

When the doctor evaluates the erythema, he may consider this a signal to request a thorough examination (such as an X-ray), which can find out if the patient has contracted tuberculosis.

Thus, if the case of tuberculosis is confirmed, treatment can be started as soon as possible to achieve a cure for the disease.

Erythema nodosum and lupus

The   lupus erythematosus, commonly known as lupus, is a disease that affects not only the skin but also the kidneys, blood vessel walls, lungs, heart, and other organs.

But its main characteristic is the appearance of erythema, reddish lesions in different parts of the body, such as on the face, on the back, etc.

Lupus is a disease in which our body produces large amounts of antibodies, causing an imbalance. This imbalance causes the defense cells to attack our own body, causing malfunction and health problems.

Other symptoms of systemic lupus erythematosus include: tiredness , fever , sudden weight loss, loss of appetite, inflammation of the skin in different places and joint pain.

What is leprous nodular erythema?

Many leprosy patients can develop an inflammatory syndrome, which is called leprosy erythema nodosum or type 2 reaction.

In which it can occur before, during or after the treatment of leprosy (condition in which it infects the skin and nerves).

The main symptoms are nerve involvement, the presence of eye lesions causing visual blurring, arthritis and inflammatory edema in the hands and feet.

Leprosy nodular erythema is one of the most common causes of morbidity in leprosy patients who do not have medical assistance, due to neural damage, paralysis and other changes that the disease can cause.

Causes of erythema nodosum

Generally, erythema nodosum appears as a symptom of another disease, but it can also appear due to allergy to any medication or to unknown causes. The diseases and conditions that can cause erythema nodosum are:


The use of some medications can cause erythema nodosum to appear throughout the body, the most common drugs to cause this condition are: sulfonamides, iodides, bromides and oral contraceptives.


One of the most frequent causes of erythema nodosum is allergies or sensitivities to various substances, including medications or external agents that invade the body.

Read more: Skin allergy: causes and how to identify symptoms


Before, during or after leprosy treatment, patients may develop an inflammatory syndrome, called leprosy erythema nodosum leprosum . This condition is characterized by the presence of red and painful nodules. In this case, leprosy is the cause of erythema.


The main characteristic of lupus is the presence of lesions (erythema) and reddish spots on different parts of the body. When they appear they are interpreted as one of the symptoms, of the presence of lupus in the patient.


The sarcoidosis is an immune response triggered by unknown factors, but attributed possibly to contact with viruses, fungi, bacteria or other external agents. This disease inflames the joints and causes painful swelling of the skin (erythema nodosum).

Inflammatory bowel disease

Inflammatory bowel diseases have not yet identified their cause, the hypothesis is that they occur due to normal bacteria in the functioning of the intestine.

Autoimmune changes or genetic predispositions cause an abnormal reaction, causing problems to the patient, one of which is erythema nodosum.

Inflammatory bowel diseases are nonspecific ulcerative colitis (UC), Crohn’s disease (CD) and undetermined colitis .


Among the different reactions that occur in the body during the gestational period, one of them is that of the skin. The erythema nodosum can appear in pregnant women, cause pain and disappear spontaneously after delivery.

Read more: What is not normal during pregnancy?


Caused by airborne bacteria, tuberculosis has one of its reactions, erythema nodosum. It can arise when a primary tuberculosis type infection occurs and mainly affects the calf.

Behçet’s disease

Behçet’s disease is characterized by an inflammation of the blood vessels, of the chronic type, which causes painful sores throughout the body. In addition to them, lesions such as erythema nodosum, inflammation of the eye, thrombosis in veins, among other symptoms , may also appear .


Some types of cancer usually bring with the symptoms erythema nodosum, they are those of the lymphoma type (which affects the lymphatic system) and leukemia (affects the cells of the bone marrow).

Risk factors

The risk factors that can influence erythema nodosum are:

  • Diabetes;
  • Malnutrition;
  • HIV;
  • Smoking;
  • Oncological treatment;
  • Kidney disease.

Symptoms and features of nodules

The nodules of erythema nodosum are usually painful, bilateral, and can resolve without ulcerations or scarring, among the characteristics of this condition are:

Pain and tenderness

When the nodules appear, they are followed by pain and tenderness when touching the lesion.

Bilateral injuries

In patients, nodules may appear on both sides of the body, making it possible to identify erythema in a simple way.

Burning and burning

When the erythema nodosum appears, it leaves a burning sensation in the region where it appeared, disturbing the patient. The joints can become swollen and also start a fever.

Color change

Erythema may appear reddish, but over the days it may change to purple or blue.

Other symptoms

In addition to skin blemishes and rashes, which can cause pain, the patient may experience other symptoms such as:

  • Physical exhaustion;
  • Fever;
  • Cough;
  • Infection of nose and throat;
  • Conjunctivitis.

How is the diagnosis made?

The diagnosis is made by a dermatologist, who will analyze the clinical appearance and will be able to confirm the result, the specialist can also request tests such as excisional biopsy of a nodule when necessary and blood test:

Clinical evaluation

The clinical evaluation consists of the doctor observing the lesion in detail, in which case the characteristics such as color, consistency, shape, distribution of the lesion, type (can be stain, scar), etc., are analyzed.

Read more: Watching injuries is not enough to diagnose skin cancer

Blood test

The blood test, although not specific for erythema, is recommended to complement the diagnosis, identifying the presence of infections, other diseases or the presence of inflammation.


A biopsy is an examination in which a small sample is taken from the site where the lesion is located. Then sent to a laboratory, which will use a microscope to investigate the cause and type of injury in greater depth.

Is there a cure?

Yes , erythema can be cured. After the diagnosis, the specialist can advise on the best medication for the case, some examples are the use of anti-inflammatory drugs , corticosteroids and antibiotics .

Resting also helps to relieve pain and reduce the size of the swelling in your legs.

In some specific cases, medications used in daily life may be suspended to check if it is not one of these drugs that is causing the problem.

What is the treatment for erythema nodosum?

The erythema nodosum can be treated with rest and the use of medications, when the cause is identified by the doctor. For the nodules, pain relief drugs are indicated, but depending on the case, the erythema may disappear spontaneously:


It is indicated to remain at rest and perform the elevation of the legs, in a place where they can be extended, such as a sofa or even in bed.

Cold compresses can relieve the pain, it is also necessary to avoid walking for a long period, so as not to make the situation worse. When resting, the erythema can heal itself between 3 to 6 weeks.

Treatment of the origin of erythema

The erythema nodosum may arise due to another condition that is manifesting in the body. When the treatment starts, the nodules will disappear spontaneously. In such cases, treatment varies according to the causing change.


In the medication part, drugs can be used to reduce inflammation, relieve pain, fight infectious agents or treat associated conditions and diseases.

Among the most used drugs for the treatment of erythema nodosum, are:

Non-steroidal anti-inflammatory drugs

Anti-inflammatories are recommended to help fight joint pain and to reduce inflammation of the nodules. They can be used:

  • Indometacina (Indocid);
  • Desloratadine ( Desalex , Aleradina , Desloratadina ).


In addition to anti-inflammatory drugs, corticosteroids can be used to decrease symptoms. Between them:

  • Dexamethasone ( Decadron , Cortidex , Dexamethasone );
  • Valerato de Betametasona ( Betnovate , Betsona, Valerato de Betametasona );
  • Prednisona ( Meticorten , Ciclorten , Prednisona ).

Potassium iodide

Potassium iodide can be recommended in cases where the lesions do not heal easily, as it helps to reduce skin reactions.

  • Potassium iodide ( Iodenax , Iodeton ).


After the diagnosis has been made and the nodule has been confirmed due to an infection of bacterial origin, antibiotics are administered, such as:

  • Bacitracin + Neomycin + Zinc ( Bacineo ).


NEVER self-medicate or stop using a medication without first consulting a doctor. Only he will be able to tell which medication, dosage and duration of treatment is the most suitable for his specific case. The information contained on this site is only intended to inform, not in any way intended to replace the guidance of a specialist or serve as a recommendation for any type of treatment. Always follow the instructions on the package insert and, if symptoms persist, seek medical or pharmaceutical advice.

Natural treatment for erythema nodosum

The home treatment does not exclude the treatment carried out with the medications, it must be done together to assist in the improvement of the patient:

Food: what to eat?

Food can help in the improvement of pain caused by inflammation, for which some anti-inflammatory foods are indicated, such as:

  • Citrus fruits in general;
  • Red fruits like the strawberry;
  • Vegetables like broccoli and cauliflower;
  • Spices like saffron, cloves, garlic.
  • Fish for being rich in omega-3.


Generally, it disappears on its own for 3 to 6 weeks, with adequate rest and treatment, without causing future complications.

In cases considered rare, the erythema nodosum can become chronic, in which the nodules can remain from 6 months to 2 years causing pain and without the cause being discovered.

Complications: is erythema nodosum severe?

In general, no. Knotty erythema alone does not cause complications and does not pose great risks to the patient. However, it is necessary to investigate the source of the problem.

Often, these are diseases that manifest erythema nodosum as a symptom. In such cases, the condition can be serious if left untreated.

Common questions

Does itchy erythema itch?

No, erythema nodosum does not cause itching, but it can cause pain in the nodules and joints of the body, leaving the region where they are most sensitive to touch.

Read more: Measles itch? 

Is it possible to clear the spots caused by erythema nodosum?

YEAH ! In most cases the spots disappear on their own without leaving any signs, but if scars remain, it is possible to clear them.

As they are caused due to a deposit of pigment, which is made in the deep layers of the skin, the dermatologist will be able to indicate the most effective and safe way to smooth this pigment, clearing and evenening the region.

Can erythema nodosum come back?

Yes, the erythema nodosum is unpredictable as it can heal and disappear it can also return to the patient several times. In such cases, it is necessary to investigate the cause further.

Can erythema nodosum be caused by contraceptives?

Although it is not as frequent as bacterial infections, it can. Other drugs also have a more frequent relationship with erythema nodosum, but it is still necessary to investigate the possibility of contraceptives being the cause of erythema.

Are panniculitis and erythema nodosum the same thing?

-Yeah . Panniculitis is a condition that can affect the entire body, erythema nodosum is one of the types of panniculitis, which predominantly affects the region of the shins and legs. Knotty erythema is classified as septal panniculitis, and can appear in different parts of the body.

Knotty erythema is a condition that appears as an alert for our body, which may indicate that another disease is developing.

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