Nummular Eczema – What It Is and How to Treat It

Nummular eczema, also referred to as discoid eczema, orbicular eczema and nummular dermatitis, is a chronic dermatologic condition that is characterised by the coin-shaped erythematous spots that develop on the patient’s skin. The word “nummular” actually originated from the Latin term for coin, as the lesions tend to take the shape of a coin. In majority of cases, such lesions are very itchy and distinct. They can be fluid-filled or become dry and flaky.

Nummular Eczema

The term nummular eczema has been used in the medical field both as a disease entity and as a description of lesion structure in various illnesses, including asteatotic eczema, atopic dermatitis, and contact dermatitis. It was initially described in 1857 by Deverigie as oval lesions on the upper extremities. For this post, we will focus on nummular eczema as a disease which has been described in medical literature.

Nummular eczema typically presents itself following a skin injury, such as an abrasion, a burn or an insect bite. It may cause a single patch or several patches of the round-to-oval lesions, which can last for several months. The lesions may vary in size and range from one to four inches. Nummular eczema is more prevalent among men and it can occur at any age. Men normally develop the lesions between the ages of 55 and 65. Women usually develop the disease during adolescence (age 13-19) or during young adulthood (age 20-35).

While the symptoms of nummular eczema can be annoying and troublesome, they can be effectively treated with antibiotics, corticosteroids, antihistamines, and topical medications. It is not hereditary and definitely not contagious, meaning it cannot be transmitted from one individual to another via direct skin contact.

Conditions that Trigger Nummular Eczema

Since nummular eczema may look like ringworm, it is imperative to ensure that it is not a fungal infection, particularly if it does not have a favorable response to medication. This can be done with a fungal culture or through skin scraping. It is also important to note that nummular eczema, just like atopic dermatitis, can be aggravated by bacterial infection, usually staphylococcus.

Seek consultation with your physician if you believe you have an infection in the area where nummular eczema appeared. You may also purchase our ebook to know the root cause of eczema and how to effectively cure it.

Eczema vs Fungal Infections

Symptoms of Nummular Eczema

The most distinctive symptom of nummular eczema is the well-defined patch of coin-shaped lesions that often appear on the arms or legs. However, there are cases when they spread to the trunk and the hands. The number lesions vary from patient to patient and could range from one to as many as 50.

Nummular Eczema Arm

The lesions differ in color, ranging from brown, to red or pink. They may burn, sting and are often itchy, which tends to worsen in the evening. The skin surrounding the lesions may be scaly or become inflamed and there can be a fetid, bad-smelling discharge. The patient may also develop fever. Nummular eczema can be painful and may cause emotional stress due to the appearance of the lesions.

If you think you have nummular eczema, seek immediate medical attention. If you leave it untreated, a secondary skin infection may develop and a yellowish crust will form on top of the infected lesions.


First, it is important to note that nummular eczema is strictly confined to the skin. It is not a systemic disease. Unfortunately, there is only little information pertaining to its pathophysiology, although it is often accompanied by dry skin or xerosis.

Just like the other types of dermatitis, nummular eczema is likely caused by a combination of an immunologic response and dysfunction of the epidermal lipid barrier – the protective structure that retains moisture. Xerosis leads to leaks in the epidermal lipid barrier and this allows allergens from outside the body to penetrate the skin and trigger an allergic reaction.This assumption is backed by a well recognized study which revealed that geriatric patients suffering from nummular eczema have heightened sensitivity to aeroallergens when compared to controls from the same age group. The compromised skin barrier may also cause increased vulnerability to allergic contact dermatitis. 

The use of certain medications had been associated with nummular eczema, since any drug that induces xerosis can potentially trigger the disease, especially diuretics and statins or cholesterol lowering medications. The outbreak of severe, generalized erythematous plaques has been reportedly linked to interferon and ribavirin treatment for hepatitis C. Other studies also implicated the use of inhibitors of tumor necrosis factor (TNF) which is a protein that plays a role in systemic inflammation and is one of the multifunctional cytokines involved in the acute stage reaction.

The onset of nummular eczema has likewise been associated with mercury in dental amalgams. It has been postulated that hypersensitivity to metals in the oral cavity may be enough to initiate an immune response that leads to the development of nummular plaques.

The possible role of mast cells is also under scrutiny due to the intense itching (pruritus) that typically accompanies nummular eczema. Researchers have documented an increase in the number of mast cells in the plaques when compared to non-lesional samples. A mast cell is one that is packed with basophil granules and is found in  large numbers in connective tissue. They release histamine and other chemicals during allergic and inflammatory reactions.

Nummular Eczema Example

One study pinned down neurogenic causes of inflammation in both atopic dermatitis and nummular eczema by studying the correlation between mast cells and sensory neurons and determining the cutaneous distribution of neuropeptides in patients with nummular eczema. The proponents of the study theorized that the release of histamine from mast cells may cause itching through their interaction with neural C-fibers. The study revealed that cutaneous contacts between nerves and mast cells increased in both lesional and non-lesional samples when compared with samples from normal controls. Moreover, substance P and calcitonin gene-related peptide (CGRP) fibers were substantially increased in lesional samples when compared to non-lesional samples. Substance P and CGRP are both neuropeptides that may trigger the release of other cytokines and mediate the inflammatory response.

Other studies showed that mast cells in the dermis may have diminished chymase activity, resulting in reduced ability to breakdown protein and neuropeptides. This dysregulation may subsequently cause decreased capability of chymase to inhibit inflammation.

Etiology of Nummular Eczema

The etiology is unknown and likely involves a number of different factors. However, a vast majority of patients dealing with nummular eczema are known to have very dry skin. Abrasions, contact with chemicals, and local trauma such as insect bites, may precede the onset of the disease.

In some cases, contact dermatitis was found to be the trigger due to its allergic or irritant nature. Sensitivity to metals like cobalt, nickel, or chromates has also been reported among patients. In one study, the researchers found that the most likely sensitizers are colophony (rosin), neomycin sulfate (an antibiotic), nickel sulfate, and nitrofurazone (often used as a topical antibiotic ointment).

Cases of nummular eczema in the past have been caused by exposure to depilating ointments containing potassium thioglycolate, glue containing ethyl cyanoacrylate, and dental amalgams containing mercury.

For lesions involving the legs, studies linked edema, venous insufficiency, and stasis dermatitis as the contributing factors.Autoeczematization or the spread of the lesions from the initial focal site, is frequently associated with the development of multiple plaques.

Nummular eczema and other kinds of eczematous eruptions have been reported after tumor necrosis factor-alpha–blocking treatment.Dermal lesions on the breast have been documented among breast cancer patients who had undergone mastectomy. In rare cases, nummular eczema has been associated with infection.

There have also been a few reports of Giardiasis, a diarrheal disease affecting the small intestine. One study showed that in patients with nummular eczema and H.pylori infection, the eradication of the latter led to clearance of the cutaneous lesions in 54 percent of the patients.


In the United States, the prevalence of nummular eczema is roughly 2 per 1,000 people. There is no documented racial predilection and the disease is more common in males than in females. Age was discussed in the previous section, but it appears that there are two peaks when it comes to age distribution. By far the most common is observed in males who are in their 60’s and 70’s. A smaller peak takes place in the second to third decade of life, and is frequently related to atopic dermatitis. This is more common in females, by up to 33 percent in one study.

How is Nummular Eczema Diagnosed?

Doctors are able to diagnose nummular eczema by looking into the medical history of their patients and visually examining their skin. They may also do a skin biopsy in order to rule out other possible conditions. The biopsy enables a pathologist to study the skin sample under a microscope to identify the cause of the lesion.

A patch test for contact dermatitis may also be performed. The test helps in determining if any specific products that the patient is exposed to could be aggravating the lesions             Nickel is the most common culprit, although perfumes, rubber, and others can be the trigger as well.

The test lasts for three days and the patch is placed on the back. It is imperative not to get the patient’s back wet because water or sweat can interfere with the patch and yield inaccurate results.

If the doctor suspects the lesions are caused by an allergic reaction, he/she may also perform an allergy test. This can include blood tests or skin tests that can identify the substances to which the patient is allergic to, if any.

Differential Diagnoses

Nummular eczema must be carefully distinguished from the following conditions:


Lesions of nummular eczema can become infected. Heavily infected or excoriated lesions can leave permanent scars. In general, lesions on the legs take longer to heal and can leave permanent macules. Pruritic cases may cause difficulty in sleeping.

Medical Treatment

The primary objectives of treatment are skin rehydration, reduction of inflammation, restoration of the epidermal lipid barrier, and treatment of infection.

Cool or lukewarm baths help rehydrate the skin and reduce itching, as long as soap is not used. Patients must be advised to bathe at least one to two times a day, followed by the application of medicated topical creams or moisturizers. The so-called “soak-and-smear” therapeutic technique is recommended as it promotes a 20-minute plain water soak every night followed by the application of petrolatum or steroid ointment to dampen the skin. It also involves the modification of cleansing habits so soap is only applied to the armpit and groin. A study revealed higher than 90 percent response in 27 out of 28 patients suffering from chronic pruritic eruptions when the technique was strictly followed as directed.

Eczema Steroid Creams

Medical practitioners have also found that wet wrap treatments are beneficial. Lukewarm water is used to moisten the skin until it is sufficiently hydrated. Each wet wrap treatment typically takes around 10 minutes.  Steroid ointment or petrolatum is then applied, followed by occlusion for about an hour with damp clothing or a sauna suit. Plastic wrap is usually used to occlude small affected areas. This regimen can be repeated 5 to 6 times daily with petrolatum. When using prescription steroid medications, patients are instructed to be extra careful because overuse of such medications can cause stretch marks and thinning of the skin.

To address inflammation, steroids are by far the most commonly used form of treatment. Topical steroids, in particular, are very effective. For less itchy, less erythematous lesions, low-potency steroids work best. But for severely inflamed lesions with itching, vesicles and intense erythema, high-potency steroids are used. Application of the medication to moisturize the skin allows for better penetration and faster healing.

Topical immune modulators such as pimecrolimus and tacrolimus also help in reducing inflammation. They are often used a couple of days after the application of topical steroids to minimize the risk of experiencing a burning sensation when applied to irritated skin. Tar preparations are also effective in decreasing inflammation, especially in thickened and scaly plaques.

Ointments are generally more effective than creams since they are more occlusive. They also protect the skin from the environment and they are more effective in retaining water. Emollients and class I-III topical steroids are only used on a short term basis. In cases of severe eruptions, oral, parenteral, or intramuscular steroids may be needed.

In certain cases where the use of steroids is not appropriate, or when the patient has used them for a long time, doctors may prescribe a non-corticosteroid topical medication like  pimecrolimus (Elidel) or tacrolimus (Protopic). These are also known as calcineurin inhibitors (TCIs) and they have been approved for use for patients two years of age or older.

When a patient has chronic, generalized eruptions, doctors often resort to the use of phototherapy. Broad or narrow band ultraviolet B is most often used, although Psoralen + ultraviolet A (PUVA) can be used in severe cases.

Sedatives or oral antihistamines may help in reducing itching and improving sleep. Doctors often refrain from using topical antihistamines as these are potent sensitizers. In particular, topical preparations with diphenhydramine and neomycin-containing medications are contraindicated.

For impetiginization or the infection of a lesion that was previously not infected, topical antibiotics may help. Oral antibiotics like cephalexin, erythromycin, or dicloxacillin must be used when there is secondary infection.

If the eruption has been resolved, continuous hydration may prevent flares, especially in dry climates. Moisturizers or petroleum jelly may be applied shortly after taking a bath or a shower.

Note that nummular eczema may be refractory to the aforementioned medications and treatments. Immunosuppressive drugs like methotrexate have been reported to be effective and safe for such severe cases.

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Medication Summary

A potent to intermediate potency steroid can be used two to four times a day to the affected areas. The medication works best when applied in ointment form instead of cream. Once the lesions heal, a lower potency steroid must be used along with a moisturizer to prevent skin atrophy

For patients with overt infection, a combination of a steroid ointment and a topical antibiotic applied twice daily is proven to be very effective. This decreases inflammation as well as colonization by staphylococcus aureus.

Severe lesions and generalized flares can be treated with dressings soaked in tap water. The dressing is then placed on top of the steroid ointment. Doctors also use oral or parenteral steroids followed by topical therapy.

In cases of secondary infection, oral antibiotics like cephalexin, dicloxacillin or erythromycin must be used. Sedating antihistamines at night may help with sleep.

What is the Prognosis for Patients with Nummular Eczema?

Nummular eczema can improve within a year if the patient receives proper treatment. However, this type of eczema is chronic and may never resolve. The lesions may heal completely while others may remit and relapse. Patients must be informed that once they develop nummular eczema, the disease is often recurrent. In order to reduce its frequency, they should avoid exacerbating factors and remember to always moisturize their skin. Pruritus or itching is often worse at bedtime and may lead to irritability and difficulty in sleeping.

Secondary infection may lead to the development of lesions with serosanguineous exudates, meaning a combination of blood and serum. For generalized flares, doctors may prescribe systemic antibiotics and/or steroids. Heightened contact sensitivity to environmental allergens (particularly metals) may restrict the ability of patients in tolerating those allergens, particularly clothing, dental amalgams, jewelry, and even occupational exposure.

As mentioned in the preceding section, the lesions in the lower extremities generally take longer to heal and can leave behind scars.


This aspect is equally important, if not, more important than the actual treatment of nummular eczema. Aggressive skin hydration may help limit the frequency between eruptions.

Bathing is obviously permitted, but the use of hot water must be avoided. Oil additives can be used in the water Patients must also use mild, non-drying soap. They must be advised to use non-soap cleansers only for hygiene and control of body odor (i.e. on the armpit, groin, and feet). An emollient must be used shortly after bathing in order to prevent drying of the lesions. The skin can be dabbed and then the emollient is applied before it completely dries out. Clothes must be loose and the fabric must be breathable in order to avoid overheating. A room humidifier may be used, as this is helpful especially when a heater or air conditioner is concurrently working. Alternatively, one must look to resolve any forms of Eczema using the elimination diet and trying to find the root cause. A best selling e-book, which has helped find the root cause and cure over 250,000 people worldwide, is sold here.