Nummular eczema and ringworm are skin conditions that can cause similar-looking rashes. Being able to tell these two conditions apart is crucial because they have different causes and treatments.
Nummular eczema, also known as discoid eczema, is a condition in which people develop red or brown areas on their skin that are coin-shaped or oval.
These spots or patches can appear on the arms, hands, legs, or torso. They can be present in clusters or may join up to form larger patches. As a result, they can range in size from 1 to 4 inches.
Other symptoms of nummular eczema may include:
- dry skin
- burning and itching of the skin, which is usually worse at night
- open spots that may crust over
If the spots become open, they are vulnerable to bacterial infection. Infected nummular eczema can cause:
- foul-smelling discharge
According to the National Eczema Association, nummular eczema most commonly affects men, usually between the ages of 55 and 65 years old. If women experience the condition, they typically notice it between the ages of 13 and 25 years old.
Doctors do not know exactly what causes nummular eczema, but some triggers and risk factors may include:
- dry skin that results from cold weather
- prior use of topical medical creams, such as isotretinoin and interferon
- 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
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.
Ringworm typically causes ring-shaped patches of skin that often affect the arms and legs but can develop anywhere on a person’s body, including:
- the soles of the feet, known as tinea pedis or athlete’s foot
- the scalp, called tinea capitis
- the groin area, known as jock itch
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
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
A doctor will diagnose nummular eczema or ringworm by examining the skin and asking about the signs and symptoms. They may ask when the rash first appeared, what makes it better or worse, and if the individual has already tried any treatments.
The doctor may also take a tissue sample from one of the patches to determine if an infection is present or to confirm their diagnosis.
Keeping the skin clean and hydrated can help treat nummular eczema. People can also prevent flare-ups and relieve symptoms by:
- 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
- keeping rooms cool and moist, possibly by using a humidifier, which may also help keep skin from drying out
- wearing soft, natural fabrics, such as cotton, to reduce skin irritation
- avoiding wool fabrics, which can irritate nummular eczema
Doctors may also prescribe topical or oral corticosteroids to treat nummular eczema. 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
In cases where nummular eczema becomes infected, a doctor may also prescribe topical or oral antibiotics.
People can treat ringworm using antifungal creams, ointments, tablets, or shampoos. Many of these medications are available over the counter (OTC).
It will usually be necessary to apply these medications to the skin for 2 to 4 weeks before the fungus will go away. It is best to see a doctor if the ringworm rash does not clear up within this time. A doctor or dermatologist can prescribe stronger antifungal medications to treat the condition if necessary.
Nummular eczema and ringworm are both skin conditions that can cause round patches of red, itchy 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 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.