The cause is unknown. Only occasionally does this turn out to be a medication allergy, although this is often considered in the evaluation. It is more common in the winter. Nummular eczema is frequently associated with dry skin. Wool, soaps and frequent bathing (more than once a day) often worsen the condition. People with eczema often have skin that is dry and easily irritated by soap, detergents, and rough clothing. Clothes washed or dried with liquid or sheet fabric softeners such as Kling, may also irritate the skin. Hot and cold weather often aggravates eczema. Certain allergies may worsen eczema, but they don't cause it. This is not the same condition as "Atopic" eczema, a much more common skin problem that can be allergic.

Unfortunately, there is no cure. However, there are effective ways of controlling it. Very strong prescription strength cortisone ointments applied to the skin are the best medicines for controlling nummular eczema. When used for an extended period of time, or over large areas of the body, periodic dermatology exams are necessary. Strong cortisone ointments shouldn't be applied to the face, armpits, groin, or rectal area. When using cortisone ointments always remember to use just a little and massage it in well. In most cases, application once daily does as much good as using it more often. For stubborn scaly nummular eczema, coal tar can be added by the pharmacist into your ointment. Although this can be helpful, it smells and stains the clothing. The sites of nummular dermatitis are prone to infection ("Staph") and often a week or two of oral antibiotics is very helpful, but avoid use of over the counter antibiotics such as "Neosporin". Severe cases can be calmed down with internal treatments of oral or injected cortisone. Persistent itch outbreaks can be controlled with ultraviolet light treatments given in the dermatology office. Unusual or severe cases can be controlled very well with the Drugs Neoral or Methotrexate, but it is rare to use these potent drugs.

In general, keep the skin lubricated. Apply oil such as neutrogena body oil or alpha-keri oil to the skin at the end of your shower. Vaseline is even more helpful if not too geasy. Do not take more than one bath or shower a day. Use lukewarm water, as hot water dries out the skin. When toweling dry pat, don't rub. Blot the skin so there is still some water left on the skin. Then apply a moisturizer to all of the skin such as Vaseline, Cetaphil cream, Complex 15, or Moisturel cream. Soap irritates and dries the skin, so keep it away from your eczema. When bathing limit the use of soap to your face, armpits, genital area, and feet. For soap, use Cetaphil, Oil of Olay, Dove or Basis. Avoid contact with wool or rough clothing. Cotton clothes, (100%) are best. When laundering the clothes, use no fabric softener, Kling or dryer sheets. Wash the clothes using dye free, fragrance free detergents such as the "All free" detergent. It is possible to find a treatment routine that lets you control your nummular eczema