Nummular dermatitis (nummular eczema) is a type of eczema characterized by pruritic, coin-shaped, scaly plaques.

Nummular dermatitis is most common in men, and the peak age of incidence is between 50 and 65 years. The second most common age of incidence is between 15 and 25 years.

The etiology of nummular dermatitis remains incompletely elucidated. While some patients have some of the signs and symptoms associated with classic atopic dermatitis, the majority of individuals with nummular dermatitis do not have a personal or family history of atopy. Venous stasis may be a predisposing factor to developing lesions on the legs, and asteatotic eczema may also have nummular plaques as part of its presentation. Additionally, around one-third of over 1000 patients with nummular dermatitis had 1 or more positive patch tests in 1 study. Nickel sulfate, potassium dichromate, and cobalt chloride were the most frequent contactants in this study.

Exudative discoid and lichenoid chronic dermatitis, also known as "oid-oid" disease and Sulzberger-Garbe syndrome, is a variant of nummular dermatitis marked by severe pruritus, chronicity, and persistence despite topical therapy. Most cases are reported to occur in adults, but cases in children are also reported.