EczemaNet Article
Nummular Eczema

Nummular eczema is a puzzling disease with at least three names: (1) nummular eczema, the most commonly used name, (2) nummular eczematous dermatitis, a longer and more medically descriptive name, and (3) discoid eczema, a name derived from the disease’s typical coin-shaped lesions seen in this photo:

Typical coin-shaped lesions of nummular eczema on the back of a patient’s hand.

(Photos used with permission of the American Academy of Dermatology
National Library of Dermatologic Teaching Slides)

The cause or causes of nummular eczema are not known with certainty, but many different causes have been suggested. A number of factors, acting alone or in combination, may be suspected—for example, dry skin in indoor and outdoor environments with low humidity; isotretinoin (a prescription medication used to treat severe acne that proves resistant to other treatments); and bacterial infections that induce a hypersensitivity reaction in skin.

Factors that may cause worsening of nummular eczema include wool clothing worn next to the skin, topical medications, soaps and detergents, and frequent bathing (as seen in this photo):

Red, crusted nummular eczema lesions on the ankle of a patient who
bathed with vigorous rubbing several times a day.

Nummular eczema characteristically appears first as a group of tiny red spots (papules) and blister-like lesions (vesicles) that enlarge and merge into a reddened, itchy, sometimes burning coin-shaped lesion two to 10 centimeters in diameter. The lesion may be uniformly red at first, then clear in the center to form a "ring" that resembles the fungal infection called ringworm.

New, acute lesions are likely to "weep" edematous fluid that dries into crusts. Chronic, persisting lesions are scaly.

An outbreak of nummular eczema may begin with one or several lesions. Some patients experience spontaneous clearing of lesions within a year. In other patients the lesions persist or recur for many years; lesions that recur after clearing tend to do so at the sites of the original outbreak.

The most common sites for nummular eczema are the legs (most common), arms and hands, and the torso. The disease is more frequent in men than in women, with a peak age of onset at 55 to 65 years. A smaller peak has been observed in women 15 to 25 years old.

Since the cause of nummular eczema is unknown, treatment is largely directed at relief of the major symptoms of itching and burning. Treatment should be prescribed by a dermatologist after a diagnosis of nummular eczema is confirmed. Baths with oil additives, and regular application of emollients can keep the skin from becoming excessively dry. Tar preparations and topical anti-inflammatory steroid agents may be prescribed to reduce inflammation and itching. Skin infection may be treated with prescribed antibiotics. Anti-histamines or ultraviolet phototherapy may be prescribed. Oral steroids may also be prescribed in severe cases that are resistant to other forms of treatment.

References:
Sotor NA. Nummular eczematous eczema. In: Freedberg IM et al (eds.) Fitzpatrick’s Dermatology in General Medicine, 5^th ed. New York: McGraw Hill; 1999:1480-1482.

Jarvikallio A, Naukkarinen A, Harvima IT et al. Quantitative analysis of tryptase- and chymase-containing mast cells in atopic dermatitis and nummular eczema. Br J Dermatol 1997; 136:871-877.

All content solely developed by the American Academy of Dermatology