Nummular eczema, also known as nummular dermatitis or discoid eczema, is a chronic but treatable condition that causes itchy coin-shaped spots to develop on the skin.
Nummular eczema often appears on dry skin, after a skin injury, or after exposure to an irritant. It typically results in one or multiple patches of coin-shaped lesions. The patches can last for several months.
These spots are often very itchy and well-defined. They may ooze clear fluid or become dry and crusty.
It develops more often in people with very dry skin and usually requires treatment to resolve.
This article will cover the causes, symptoms, and treatment options for nummular eczema.
Researchers have not yet identified the exact cause of nummular eczema. However, many people with the skin condition have a personal or family history of:
- atopic dermatitis, or eczema
- allergies
- asthma
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
- medications that cause dry skin
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 may eventually spread to the torso and hands. They may be brown, pink, red, or purplish, depending on your skin color.
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Symptoms of nummular eczema may include:
- coin-shaped lesions that are very itchy and burn
- lesions that ooze fluid and eventually crust over
- scaly or inflamed skin around the lesions
Nummular eczema can also lead to a skin infection requiring urgent medical treatment. Symptoms of a skin infection can include:
- yellow or golden crusts
- streaks of red or brown
- swelling
- pus
- pain or tenderness in the affected area
When nummular eczema begins to heal, the spots may become flatter. You may also have skin color changes known as postinflammatory hyperpigmentation (skin darkening) or hypopigmentation (skin lightening) around the flat spot. This tends to occur more often in people with skin of color and can last for several months.
If nummular eczema returns, 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.
Nummular eczema lesions can look similar to ringworm, which is a fungal infection of the skin.
Ringworm (tinea corporis) also tends to cause itchy bumps that become 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 can be very itchy. Ringwork tends to go away with
A dermatologist can perform an exam and tell the difference between these two conditions and other conditions, like psoriasis, that may look similar.
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A doctor may be able to diagnose nummular eczema by asking you about your medical history and visually inspecting your skin. They may also take a skin sample by superficially scraping the skin to check for ringworm. They may look under a microscope to see if there is fungus present.
If you have a biopsy, a dermatopathologist may also analyze the skin cells 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 also perform an allergy test. 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.
Though the symptoms of nummular eczema can be bothersome, you can treat it with medications and lifestyle changes. It is not contagious, which means you cannot get it from another person through direct skin contact.
Medications
Over-the-counter medications may not be strong enough to relieve the symptoms of nummular eczema.
You may also need to see a doctor to rule out other skin disorders that can look like nummular dermatitis.
A healthcare professional such as a dermatologist can also prescribe medications to treat nummular eczema. These may include:
- prescription-strength corticosteroid
- antihistamines
- tacrolimus ointments
- pimecrolimus cream
- coal tar cream
If symptoms do not go away even after medicated treatment, your symptoms may be due to an allergic reaction. Your doctor may then recommend a patch test to identify the source of the allergy.
Lifestyle changes
There is no cure for nummular eczema. However, you may be able to manage your symptoms with certain lifestyle measures and by avoiding triggers.
Doctors may recommend avoiding:
- wool or other irritants that may trigger your symptoms
- excessive bathing and hot water
- harsh soaps
- stressful situations
- environmental irritants, such as household cleaners and chemicals
- scrapes, cuts, and abrasions on the skin
The following can help relieve your eczema:
- using moist bandages to cover and protect 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
- moisturizing daily
- using unscented fabric softener and dryer sheets
Be sure to talk with your healthcare professional before making changes to your treatment plan.
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 highly processed foods and 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.
Foods to eat
Some examples of foods that are health-promoting and possess anti-inflammatory properties may 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, which contains healthy monounsaturated fats
- fruits, vegetables, and whole grains, which contain antioxidants and healthy carbohydrates
- turmeric and ginger, which may have some anti-inflammatory properties
Foods to avoid
Examples of inflammatory foods to avoid or limit include:
- foods high in unhealthy oils, margarine, and fried foods such as french fries
- red meats, full-fat dairy, the skin of poultry, and butter, which all contain unhealthy saturated fat
- foods high in added sugar and refined carbohydrates, which include highly processed foods
For more specific guidelines on a personalized eating lifestyle, speak with your doctor to learn more about health-promoting eating and lifestyle eating patterns.
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 case.
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Histidine 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.
Nummular eczema tends to occur more often in males than in females. Males usually have their first episode after age 50 and females before age 30, according to the American Academy of Dermatology Association (AAD). Some children with severe atopic dermatitis may develop nummular eczema.
The following conditions may increase your risk of developing nummular eczema, according to the AAD:
- living in a cold, dry climate
- dry skin
- reduced 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
With the proper treatment and management, nummular eczema may improve or go away.
However, it can be a chronic condition in some people, so it may never fully 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.