Nummular eczema and ringworm are skin conditions that can cause similar-looking rashes. Nummular eczema can occur with dry skin or exposure to an allergen. Ringworm is a fungal infection.

This article examines the symptoms and causes of nummular eczema and ringworm.

It also explains their differences and similarities and looks at how doctors diagnose the conditions.

We also examine the various treatment options available, as well as answer some common questions about nummular eczema and ringworm.

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Nummular eczema, also known as discoid eczema, is a condition in which people develop itchy, inflamed circular patches on their skin. It tends to occur in people with extremely dry skin

In some cases, a person who experiences other types of eczema may also get nummular eczema. For example, a person living with contact dermatitis can develop nummular eczema after exposure to triggers such as chemicals in cosmetics.

What does nummular eczema look and feel like?

People with lighter skin usually develop red or brown areas on their skin. People with darker skin can develop dark brown patches, or they may develop patches that are lighter than their surrounding skin.

The rash appears as a round, coin-shaped, or oval patch in both cases. “Nummular” comes from the Latin term for “coin.”

These spots or patches can appear on the arms, hands, legs, or torso. They may be present in clusters or join up to form larger patches. As a result, they can range in size from a fraction of an inch to about 4 inches.

Other symptoms of nummular eczema may include:

  • dry skin
  • burning and itching of the skin, which is often worse at night
  • open spots that may crust over

With treatment, the spots can heal and rarely scar over. On lighter skin, they may leave temporary areas of pale skin. On darker skin, the lesions can leave areas of hyperpigmentation or darker patches.

If the affected skin is open, it can become vulnerable to a bacterial infection. Infected nummular eczema may cause:

  • redness
  • swelling
  • foul-smelling discharge
  • fever

Who gets nummular eczema?

Nummular eczema affects both males and females, but its occurrence varies by age. Females typically develop the condition from the age of 15–25, while males typically develop it from the age of 50–65.

What triggers nummular eczema?

Doctors do not know exactly what causes nummular eczema, but some triggers and risk factors include:

  • dry skin that results from cold weather
  • prior use of medications such as interferon, statins, or diuretics
  • a history of atopic eczema or other allergic conditions
  • injuries to the skin, such as burns, insect bites, or scrapes
  • poor blood flow to the legs

Learn more about nummular (discoid) eczema here.

Ringworm, also known as tinea corporis, is a skin condition that can closely resemble nummular eczema. Despite the name of this condition, it is a type of fungus, rather than a worm, that is responsible for causing it.

It typically leads to ring-shaped patches of skin that often affect the arms and legs but can develop anywhere on a person’s body, including:

What are the symptoms of ringworm?

The symptoms of ringworm include:

  • round, flat patches of red, pink, brown, or gray skin
  • patches that may be lighter or clear in the center, making them appear ring-shaped
  • patches that grow slowly and may spread to other areas of the body
  • itching

While medical research often describes the rash as reddish in color, this typically refers to lighter skin tones. The rash can appear brown, gray, purplish, or lighter than the rest of the skin.

What are the risk factors for getting ringworm?

Ringworm typically causes less severe symptoms than nummular eczema. However, unlike nummular eczema, ringworm can spread between people. Risk factors for getting ringworm include:

  • playing contact sports
  • sharing towels, clothes, or razors with other people
  • failing to wash and properly dry the feet after being barefoot in locker rooms or pool areas
  • living with diabetes
  • obesity
  • sweating heavily
  • close contact living, such as in barracks
  • clothing that chafes the skin
  • spending time in a tropical or humid environment

Learn more about ringworm here.

A doctor will diagnose nummular eczema or ringworm by examining the skin and asking about signs and symptoms. They may ask when the rash first appeared, what makes it better or worse, and if the person has already tried any treatments.

If a physical exam is not enough, a doctor may also take a tissue sample from one of the patches to determine if an infection is present or to confirm their diagnosis.

Diagnosis challenges

People with darker skin tones may want to ask their doctor about their experience with identifying skin conditions on dark skin tones.

In a 2018 study, researchers noted that darker skin tones in four major medical textbooks made up only about 4.5% of photos.

In other words, doctors may not be well versed in what a rash, such as ringworm, looks like on darker skin tones.

Unlike other forms of eczema, a doctor will need to more aggressively treat nummular eczema to help ensure it clears and prevent its recurrence. There is currently no cure, but with treatment and preventive steps, a person can help stop flares from occurring.

A doctor may prescribe topical corticosteroids along with topical antibiotics to treat nummular eczema. They may also recommend using an astringent compress if there is drainage in a person’s skin, which can help dry the area and prevent staph infection.

Other treatment options include:

  • coal tar cream
  • phototherapy, which involves exposing the skin to ultraviolet (UV) light
  • topical calcineurin inhibitors, such as tacrolimus or pimecrolimus
  • antihistamines, such as hydroxyzine or diphenhydramine (Benadryl)
  • systemic immunosuppressants, such as methotrexate

People can also take some preventive steps to help stop flare-ups and relieve symptoms, such as:

  • using gentle soaps, which are less likely to dry out the skin
  • applying fragrance-free moisturizers that protect the skin from damage, such as moisturizing body oils and petroleum jelly
  • reducing stress
  • keeping rooms cool and moist, possibly by using a humidifier, which may also help keep skin from drying out
  • wearing loose-fitting clothing
  • drinking alcohol in moderation only
  • keeping the skin protected from injury or contact with harsh chemicals

People can treat ringworm using antifungal creams, ointments, tablets, or shampoos. Many of these medications are available over the counter or as prescriptions. The exact form a dermatologist may recommend will vary according to the location of the ringworm.

It will usually be necessary to apply these medications to the skin for anywhere from 2–4 weeks before the fungus will go away.

The following sections provide answers to some common questions about nummular eczema and ringworm.

Can I cure nummular eczema?

Nummular eczema has no cure. However, treatment can help reduce the severity of flares and prevent new flares from occurring. Following treatment recommendations, avoiding triggers, and keeping the skin hydrated can all help.

Is ringworm dangerous?

Ringworm is a common skin condition that affects many people as athlete’s foot or jock itch. While it does not necessarily cause dangerous side effects, it can spread to other areas of the body and the initial rash may increase in size if a person does not treat it.

It is also highly contagious, which means a person can easily pass it on to others.

How do you know if you have ringworm?

Ringworm often creates a ring-shaped rash with a raised, scaly border that snakes its way around the edge like a worm. Some experts believe that the appearance may be where it got its name.

The rash is typically itchy and can cause discomfort. A person should talk with their doctor about getting a diagnosis if they suspect ringworm.

Nummular eczema and ringworm are skin conditions that can cause round patches of itchy skin that vary in color depending on the tone of a person’s skin.

However, these conditions have different causes and treatments, so it is important to be able to differentiate between them.

Nummular eczema typically causes coin-shaped patches, while ringworm often produces ring-shaped patches.

Ringworm is a fungal infection that can spread between people. It is usually treatable with antifungal medications and should clear up within a couple of weeks.

Nummular eczema is an inflammatory skin condition. There is currently no cure for nummular eczema, but keeping the skin hydrated, avoiding known triggers, and using eczema medications can relieve symptoms and help prevent future flare-ups.