Nummular dermatitis is a chronic skin condition that manifests as small, round, itchy patches. A person may have only one patch of affected skin or several lesions on the hands, arms, legs, or elsewhere on the body. The condition is most commonly seen in men over the age of 70, but nummular dermatitis can appear at any age. Doctors do not fully understand why it occurs, but several risk factors such as dry skin and chemical exposure have been identified. In most cases, itching and pain can be relieved with over-the-counter topical creams and moisturizing lotions.

Lesions associated with nummular dermatitis are usually round or oval shaped, red, and very dry. The center of a sore is usually lighter colored than the edges, creating a ring-like appearance. The skin tends to crack and become scaly around the perimeter of the lesion. Chronic itching and burning sensations are common with nummular dermatitis, but doctors warn against scratching them to avoid breaking open the skin. If a patch becomes infected, a blister can form that oozes yellow pus and crusts over after several days.

The causes of nummular dermatitis are unknown, but many different potential triggers may contribute to outbreaks. Many people who acquire the condition already have chronically dry skin, allergies, and familial histories of skin problems. Some cases appear to be triggered by exposure to industrial chemicals or certain metals, including cobalt and nickel. Any condition that dries out and irritates the skin can make episodes more likely to occur, such as very cold and dry weather, hand soaps, and tight-fitting clothing.

A doctor can usually diagnose nummular dermatitis simply by inspecting the affected patches of skin. He or she may decide to collect a sample of tissue to test for infections, cancer, or other possible causes of irritation. After making a diagnosis, the doctor can apply a topical medication to soothe pain and itching. Large lesions may be bandaged to protect them and reduce the likelihood of bacterial infections. Patients are generally instructed to keep their skin hydrated with lotions to promote faster healing.

There is no cure for nummular dermatitis, and it is likely that a person who experiences an outbreak will have recurring skin problems. Doctors usually recommend that patients try to take preventive measures against future episodes. The goal of prevention is to keep the skin moisturized. Using lotion and avoiding direct skin exposure to wind, chemicals, and irritating soaps reduces the chances of nummular dermatitis returning.