Discoid eczema — also known as nummular eczema or discoid dermatitis — is a chronic condition involving inflammation of the skin. It produces a rash of coin-shaped disks that are raised, itchy, and discolored. Home remedies and light therapy may help.
Discoid eczema plaques affect different body parts, but they mostly occur on the lower legs, hands, and forearms.
Discoid eczema is a chronic condition that is long-term or recurrent. It is not contagious, meaning that it cannot pass from one person to another.
This article outlines the causes, symptoms, and treatment of discoid eczema.
Moisturizing daily with emollients is the main treatment for discoid eczema. Several over-the-counter (OTC) preparations are available, but if these do not work, a doctor may offer another solution.
People can also use a dressing soaked in flurandrenolide during the night.
Other treatment options include:
- topical steroids
- prescription nonsteroidal topical medicines
- systemic oral or injectable steroids
- biologics, such as dupilumab (Dupixent)
If milder treatments do not work, doctors may prescribe oral steroids for general symptom management. Steroid injections may also help against stubborn lesions in a localized area. People should only use steroids sparingly and according to the prescribing doctor’s instructions.
A doctor may also prescribe antibiotics, such as doxycycline (Doryx) or minocycline (Minocin), to treat secondary infections.
According to the American Academy of Dermatology Association (AAD), discoid eczema tends to appear at an older age in males than in females. It usually affects males aged over 50 years but develops in females before the age of 30 years.
Doctors do not know the exact cause of discoid eczema, but it is more likely to affect people who have dry, sensitive skin. Strong soaps, detergents, and rough clothing can all irritate the skin.
Discoid eczema appears to be more common during the winter months when indoor humidity levels are lower.
Certain medications may increase a person’s risk of developing discoid eczema. These include:
- interferon
- ribavirin
- tumor necrosis factor-alpha (TNF-alpha) blockers
- statins
Discoid eczema may cause round or oval plaques consisting of small raised spots and skin scaling. The patches are generally 2–10 centimeters in diameter, and a person may have between one and 50 of them.
The affected areas will appear discolored and have well-defined edges. On top of the coin-shaped plaques, there may be small scales or crusts.
On light skin tones, this discoloration may appear pink or red, while on dark skin tones, it may be dark brown, gray, or purple.
Learn more about how eczema appears on dark skin.
Irritation
The affected areas are extremely itchy, especially at night, and they may burn or sting.
Constant scratching and rubbing can lead to a process of lichenification, in which the epidermis, or outer layer of skin, becomes overgrown. This causes the skin to thicken and exaggerated skin markings to appear.
If the skin barrier breaks, there is a risk of infection. A viral or bacterial infection may cause weeping sores.
People may confuse nummular dermatitis with other similar skin conditions, including ringworm.
Ringworm refers to a group of fungal infections, including athlete’s foot. One type, tinea corporis, may resemble discoid eczema.
Whereas ringworm is a fungal infection, the cause of discoid eczema is unknown. However, it is more likely to develop in people with very dry skin. In contrast, ringworm can affect any type of skin.
Discoid eczema starts as clusters of small spots that turn into a rash. Ringworm is a circular patch that grows and becomes lighter in the middle, forming a ring. Several rings may form across the body. Both rashes can itch, but discoid eczema can also cause a burning sensation.
A person should ask a doctor to look at the rash, as a correct diagnosis will make the appropriate treatment possible.
Learn more about the differences between discoid eczema and ringworm.
There is no cure for discoid eczema, but treatment can help relieve the symptoms by rehydrating the skin, reducing inflammation, and preventing repeat infections.
People with discoid eczema may be able to minimize discomfort by:
- bathing or showering once a day in cool or lukewarm water
- moisturizing the skin twice daily and after showering
- practicing good hand hygiene to prevent infection
- avoiding scratching or rubbing the lesions to prevent permanent scars and infections
- applying topical steroids directly to the skin to reduce inflammation
- using tar preparations to reduce inflammation in older, thickened, scaly plaques
- trying to stay in a cool, moist environment and avoiding hot, dry surroundings that worsen the symptoms
- using an emollient cream, lotion, or soap substitute to soften and smooth the skin
- using wet wraps, such as dampened bandages, to relieve inflamed patches
If commercial products do not work, a doctor or pharmacist can advise about alternatives. Various OTC medications are available, including shampoos, emollient products, and some low dose topical steroids.
Artificial ultraviolet A (UVA) or UVB light therapy may help reduce symptoms. This therapy involves the targeted application of concentrated UV light to affected areas. People with eczema may require multiple phototherapy treatments to get the best possible results.
Complementary treatments for atopic eczema and discoid eczema include aromatherapy, massage, homeopathy, and some herbal remedies.
Before using any new complementary or alternative therapies, people should check with a doctor to ensure that the treatment is research-backed and comes from a reputable source. They should also inform the doctor about any complementary treatments they are already taking.
A doctor may diagnose discoid eczema after seeing the hallmark signs and symptoms, and they may refer the person to a dermatologist or skin specialist.
Healthcare professionals may analyze tissue samples from lesions to rule out ringworm.
If there appears to be a secondary infection, the doctor will take a swab for analysis.
People can take steps to reduce the chance of discoid eczema coming back. These include:
- hydrating the skin by using moisturizers and adding oils to the bath
- patting the skin dry gently with a soft towel after bathing
- wearing loose clothing that does not irritate the skin and choosing natural rather than manufactured fabrics
- trying an air humidifier in the home
- using a laundry detergent that does not irritate the skin and double rinsing to remove harmful chemicals that may remain on the laundry
- following the doctor’s instructions and recommendations carefully
- avoiding hot baths or showers that may dry out the skin
- refraining from scratching or rubbing the skin
Discoid eczema, also known as nummular eczema, typically causes disk-shaped patches of inflammation and skin dryness.
Using emollient ointments, maintaining good hygiene practices, and avoiding triggers can help people manage discoid eczema at home. In severe cases, doctors may recommend medical treatments, such as prescription ointments, steroid treatments, or phototherapy.