Nummular eczema (dermatitis) and ringworm are both skin conditions that can cause redness, itchiness, and other symptoms. People sometimes confuse these conditions because they can both cause circular rashes on the skin.
But the causes, risk factors, and treatments are completely different.
Nummular eczema has these additional symptoms:
- Dry skin all over the body.
- Tiny red spots that turn into large rashes across the skin. Some patches may be larger than 4 inches. These may also be round.
- Patches on the skin that vary in color: While many are red, they can also be brown, pink, or yellow. Yellow patches that are crusty may mean infection.
- Mild to severe itchiness: In some cases, nummular eczema might keep you up at night scratching.
- Burning sensations in the affected patches.
Ringworm doesn’t cause as many symptoms as nummular eczema. Most notably, the condition appears as red rings along the skin. It’s common to have just one spot of ringworm, while nummular eczema often has multiple patches.
Ringworm is sometimes mistaken for forms of eczema and other skin conditions, like psoriasis. Unlike nummular eczema, the affected areas don’t vary in color, and the patches don’t burn and sometimes don’t even itch.
Nummular eczema and ringworm also have different causes and risk factors.
The cause of nummular eczema is unknown. It tends to develop after an injury to the skin, such as a scrape or cut. There are also risk factors that are thought to contribute. These include:
- a history of excessive dry skin
- skin sensitivity
- cold, low-humidity environments
- a history of other forms of eczema, such as atopic dermatitis
- age and gender
- certain prescription acne medications
- bacterial skin infections
Though it can occur at any age, nummular eczema is most common in men ages 55 to 65, according to the American Academy of Dermatology. Women are at higher risk in their teens and young adult years.
Despite the name, ringworm isn’t caused by worms. It’s caused by a fungal infection. The condition is also called tinea corporis.
This type of fungal infection can be spread between people. Sharing hygiene products or bathing tools and going to public places like swimming pools can increase the risk.
You can get ringworm from infected animals, especially cats. You may also get it from gardening in soil that has the fungus. There isn’t always a way to identify the fungus until you’ve been exposed and start having symptoms.
Ringworm can occur in people of all ages. Children may be at higher risk because of accidental poor hygiene choices. People who spend a lot of time in gyms and public swimming areas may also be at higher risk.
You’ll need to see your doctor for a diagnosis of either condition.
It’s best to have nummular eczema diagnosed by a dermatologist. A doctor specializing in skin conditions (dermatologist) or even your primary care doctor can help determine a treatment plan and rule out other conditions.
Nummular eczema is diagnosed with a physical exam. A doctor can usually make a diagnosis by looking at the skin. Nummular eczema is most prominent in these areas of the body:
If you have open sores within any of the rashes, your doctor may take a sample to see if you have an infection. This is especially important if your symptoms look like ringworm.
A sample can help them determine if you have a staph infection from eczema, or if it’s a fungal infection related to ringworm.
Red, circular rashes on the skin are a telltale sign of ringworm, but your doctor may also test a sample to confirm. They’ll look for signs of a fungal infection. If the fungal test is negative, then you don’t have ringworm.
Once you have an accurate diagnosis, your doctor can explain treatment options.
Treating nummular eczema depends on the severity of the condition. Lifestyle changes are sometimes enough to help clear the skin. The following tips can often help:
- Avoid chemicals and metals if your condition is caused by a sensitivity to them.
- Stay hydrated to help clear up skin patches while preventing new ones.
- Bathe only in lukewarm water. A few minutes after, apply a fragrance-free moisturizer.
- Use a humidifier in your bedroom if you live in a dry climate or run the heater in your home less often.
- Wear loose cotton clothing to reduce skin irritation.
Lifestyle changes may not be enough to clear up this type of eczema. Severe cases may require one or more of the following medical treatments:
- antibiotics for skin infections
- antihistamines to combat itching, which may also help you sleep better at night
- prescription corticosteroid ointments to reduce swelling or inflammation
- oral or injectable corticosteroids
- medicated bandages
- phototherapy or light treatment
Ringworm may be treated with different types of antifungals, particularly if it affects the scalp. Oral antifungals, such as griseofulvin (Grifulvin V, Gris-Peg), may be taken by mouth. Your doctor may also prescribe topical antifungal ointments.
Some antifungal ointments are also available over the counter, such as those containing the active ingredients ketoconazole and clotrimazole. These include Lotrimin AF, Cruex, and Desenex. These are usually sufficient for treating ringworm of the skin.
However, you should call your doctor before self-medicating for ringworm. If you have another condition, like nummular eczema, it won’t respond to antifungals, though they probably won’t make the rash worse.
Ringworm, on the other hand, shouldn’t be treated with topical corticosteroids (as nummular eczema is) as these can make ringworm worse.
Ringworm may also be managed and prevented through changes to your personal hygiene routine. These habits can be helpful:
- Shampoo and bathe every day.
- Wear shoes or sandals in public places, including locker rooms and public pool areas.
- Change clothing every day, including socks.
- Avoid sharing hats and hygiene tools such as loofahs and combs.
Nummular eczema may take longer to treat than ringworm does. It may clear up within a year, though there’s a risk that it could return.
Patches and sores on the lower body can take longer to clear up, and some people experience scarring. For many people, nummular eczema doesn’t cause lasting issues compared to other forms of eczema.
For ringworm, most people see improvements after just a few weeks of treatment. Sometimes it takes up to six weeks. Ringworm isn’t usually a recurring problem, but it may come back if you don’t make changes in personal hygiene.