Nummular dermatitis, also known as discoid eczema, is a persistent rash that sometimes develops after a skin injury.
Causes of Nummular Dermatitis
Nummular dermatitis is seen more often in men than women. Men typically experience their first outbreak around ages 55 to 65, but the rash is seen much earlier in women – usually between 15-25 years of age.
The exact cause of nummular dermatitis is not clear, but it is thought to be associated with sensitivity to metals, formaldehyde and medications.
Like other types of eczema, nummular dermatitis occurs more often in cold, dry climates. It is also more likely to be seen in individuals who have been diagnosed with atopic dermatitis or stasis dermatitis, who have impaired blood flow to the legs, who have sustained an injury (such as a chemical burn or insect bite), or who are taking certain medications including interferon or isotretinoin.
Symptoms of Nummular Dermatitis
The main symptom of nummular dermatitis is a coin-shaped skin patch that develops on the legs, arms, hands, feet or body. Groups of tiny, weepy blisters form eventually spreading into round, red skin patches. Characteristics of the coin-shaped rash:
Patches range in size from 1 to 4 inches
Skin rash produces itching and burning, which can be intense
Rash ranges in color from pink to red or brown
Over time, the patches become crusty and scaly
Treatment of Nummular Dermatitis
Since nummular dermatitis can be persistent, the condition requires treatment by a qualified dermatologist. Depending on severity of the rash, treatment may include:
Corticosteroid ointment, cream or oral medications
Antibiotics (if infection is present)
Antihistamines to relieve the itch
With treatment, the rash can resolve completely. However, long-term treatment may be needed, since the patches can persist for months or years. Sometimes the skin rash in nummular dermatitis goes away only to return later.
To prevent worsening of the rash, it’s important to avoid skin injury, shower or bathe daily with lukewarm water, apply skin moisturizer at least once a day, and use room humidifiers to reduce environmental dryness.