Nummular eczema, also known as nummular dermatitis or discoid eczema, is a chronic condition but treatable condition that causes coin-shaped spots to develop on the skin. These spots are often very itchy and well-defined. They may ooze clear fluid or become dry and crusty.

Nummular eczema often appears after a skin injury, such as a burn, abrasion, or insect bite, but there are also other causes. The condition may result in one patch or multiple patches of coin-shaped lesions. The patches can last for several months.

Nummular eczema tends to occur more often in men than in women. Men usually have their first episode after age 50 and women before age 30, according to the American Academy of Dermatology Association (AAD). Some children with severe atopic dermatitis (AD) may develop nummular eczema.

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Nummular eczema is characterized by coin-shaped lesions of dry skin.
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Nummular eczema on darker skin.
Mohammad2018, 2018/Wikimedia Commons

Though the symptoms of nummular eczema can be bothersome, they can be treated with medications and lifestyle changes. It is not contagious, which means you cannot get it from another person through direct skin contact.

Medications

In some cases, OTC medications may not be strong enough to relieve the symptoms of the condition.

You will need to see a healthcare professional such as a dermatologist for prescription-strength corticosteroid or tacrolimus ointments, or pimecrolimus cream. Another option is tar cream.

You may also need to see a doctor to rule out other skin disorders that can look like nummular dermatitis.

If symptoms do not go away even after medicated treatment, your symptoms may be triggered by an allergic reaction. Your doctor may then recommend a patch test to identify the source of the allergy.

Lifestyle changes

There is not a cure for nummular eczema. However, you may be able to manage your condition by making certain lifestyle changes and avoiding triggers.

To help manage your nummular eczema, try to avoid:

  • wool and other irritants that may trigger your symptoms
  • excessive bathing and hot water
  • using harsh soaps
  • stressful situations
  • exposure to environmental irritants, such as household cleaners and chemicals
  • getting scrapes, cuts, and abrasions on the skin

The following can help relieve your eczema:

  • using moist bandages to cover and protect the affected areas
  • taking antihistamines to relieve itching and discomfort
  • applying medicated lotions or skin ointments, such as corticosteroids
  • getting ultraviolet light treatment for severe itching
  • hydrating skin with a non-scented moisturizer after showering
  • moisturize daily, especially on the legs
  • using unscented fabric softener and dryer sheets from brands such Free & Clear

Be sure to talk with your healthcare professional before making changes to your treatment plan.

The most common and noticeable symptom of nummular eczema is a patch of coin-shaped lesions on the body. The lesions frequently develop on the arms or legs, but they may eventually spread to the torso and hands. They may be brown, pink, or red.

Other symptoms may include:

  • lesions that are very itchy and burn
  • lesions that ooze fluid and eventually crust over
  • red, scaly, or inflamed skin around the lesions

Signs of eczema clearing or new flare-ups:

  • Flatter spots are visible.
  • Skin discoloration is present in the area where the spot flattens. In dark skin, this discoloration is known as postinflammatory hypopigmentation and may last for several months.
  • A new flare-up may show up as a large, raised patch on top of an old, healing spot instead of a coin-shaped lesion.

Call your doctor if you believe you have nummular eczema. If it’s left untreated, a secondary skin infection could develop. Once this occurs, a yellowish crust will form on the infected lesions.

As they progress, nummular eczema lesions can resemble another condition caused by the ringworm fungus.

Ringworm (tinea corporis) also tends to present itchy bumps that turn into round, itchy, and scaly patches with a clear center. They may look red or pink on lighter skin, or brown and gray on darker skin. Both types of lesions will be very itchy. Ringworm lesions tend to heal from the center first.

A dermatologist is a specialist trained in knowing the difference between these two conditions, and other conditions, like psoriasis, that have similar presentations.

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Ringworm often has an area of central clearing with a ring of red surrounding it.
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Ringworm is a fungal infection that can occur anywhere on the skin. Zay Nyi Nyi/Shutterstock

Nummular eczema has no known cause. However, many people with the skin condition have a personal or family history of:

Atopic dermatitis is a skin condition that causes itchy or scaly rashes. People with nummular eczema also tend to have sensitive skin that gets irritated easily.

The following factors may also contribute to the development of nummular eczema:

  • temperature changes
  • stress
  • dry skin
  • environmental irritants, such as soaps, metals, and formaldehyde
  • surgery

Currently, there isn’t a specific diet for nummular eczema. Generally speaking, people with eczema may want to consider eating a nutrient-rich, balanced diet and doing their best to maintain a moderate body weight.

Guidelines broadly suggest avoiding or limiting the highly processed foods that are common in the culture of the Western diet, as well as most allergy-causing foods, as these may have an association with eczema flare-ups.

One way to do this is to follow an anti-inflammatory diet. This diet can help you know which foods to eat and which to limit or avoid.

Foods to eat

Some examples of foods that are health-promoting and possess anti-inflammatory properties include:

  • fish containing omega-3 fatty acids, such as sardines, mackerel, tuna, herring, or supplementation via fish oil supplements
  • plant-based omega-3 sources, such as flaxseed oil or ground flaxseeds, walnuts, and green leafy vegetables
  • olive oil and canola oil, which contain healthy monounsaturated fats
  • fruits, vegetables, and whole grains, which contain antioxidants and healthy carbohydrates
  • turmeric and ginger spices, which may have some anti-inflammatory properties as well

Foods to avoid

Examples of inflammatory foods to avoid or limit include:

  • trans fats such as hydrogenated oils, which describes things like margarine and fried foods such as french fries
  • red meats, full-fat dairy, the skin of poultry, butter, which all contain unhealthy saturated fat
  • omega-6 fatty acids, which mainly comes from vegetable oils such as corn or cottonseed
  • foods high in added sugar and refined carbohydrates, which includes highly processed foods

For more specific guidelines on a personalized eating lifestyle for you, speak with your doctor to learn more about health-promoting eating, lifestyle eating patterns, and weight management.

Research on nummular eczema diet

When it comes to nummular eczema specifically, a 2021 study showed that a gluten-free diet may help you manage the symptoms of the condition.

In this case, an 11-year-old girl was able to remain completely symptom-free while avoiding all gluten. However, more research is needed to confirm whether this is true beyond this single case.

A 2020 study also showed there may be some benefit to L-His supplementation (LHS). This is a supplement containing the amino acid histidine, which the body metabolizes into histamine.

Histamine is an amino acid involved with growth and immunity. The research shows it may improve the symptoms of severe nummular eczema that is resistant to other treatments.

The following conditions may increase your risk of developing nummular eczema, according to the AAD:

  • living in a cold, dry climate
  • dry skin
  • poor blood flow or swelling in the legs
  • having another type of eczema
  • a skin injury, such as an insect bite or abrasion
  • surgery
  • some medications

Your doctor may be able to diagnose nummular eczema by asking you about your medical history and visually inspecting your skin. They may also order a skin sample to be taken by superficially scraping the skin.

A dermatopathologist will analyze the skin cells and try to determine whether the rash is nummular eczema or another skin condition.

If your doctor suspects the lesions are a result of an external allergic reaction, they may perform an allergy test as well. This test is done in the doctor’s office. It involves leaving a patch on your skin for several days and watching for a reaction.

With the proper treatment, nummular eczema may improve within 1 year. However, this is a chronic condition, so it may never resolve. Some lesions may go away completely, while others may come and go.

Lesions on the thighs, legs, and feet often take longer to heal and may leave behind darker or lighter spots. It’s best to avoid triggers that make your symptoms worse.