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Eczema types: Nummular eczema causes

What causes nummular eczema?

Researchers continue to look for the exact cause.

While studying this disease, they have discovered that nummular eczema seems to appear after something triggers it.

In studies, the most common triggers include:

  • Intense stress

  • Dry air

  • Heat and humidity

  • A skin injury, like a bug bite or scrape

  • A skin infection

  • Drinking alcohol heavily

  • Starting a medication that can cause extremely dry skin

The findings from these studies also indicate that people who develop nummular eczema have extremely dry skin. It seems that their skin was either already extremely dry or something recently made their skin excessively dry.

Extremely dry skin is dehydrated skin

Researchers believe that skin dryness plays a role in causing nummular eczema.

Close-up of severely dry skin

You can develop excessively dry skin during winter when the humidity in the air drops or when taking a medication that can dry out your skin.

Medications that come with a possible side effect of xerosis (extremely dry skin) include:

  • Diuretics, often prescribed to treat high blood pressure

  • Immunoglobulin, given by intravenous injection (IV)

  • Interferon and ribavirin, two medications prescribed together to treat hepatitis C

  • Statins, cholesterol-lowering medication

Who gets nummular eczema?

This type of eczema most commonly develops during these ages:

  • After 50 years of age (men)

  • Before 30 years of age (women)

Children rarely develop nummular eczema. A few children living with severe atopic dermatitis (AD) have developed nummular eczema. Skin with severe AD can be excessively dry, even in children. This may play a role in causing nummular eczema in children.

Certain pre-existing diseases may also increase the risk of developing nummular eczema. Researchers found that patients were more likely to develop nummular eczema if they had one of the following:

When contact dermatitis develops from a hypersensitivity to a metal like nickel, cobalt, or chromate, the risk of developing nummular eczema increases. A hypersensitivity to mercury, a metal found in older dental fillings, may also trigger the immune system to react and lead to nummular eczema.

While studying nummular eczema, researchers also discovered another key finding: Nummular eczema rarely clears without treatment.

It can take time to find an effective treatment. Because dermatologists specialize in treating skin disease, seeing a board-certified dermatologist can be a big help. Board-certified dermatologists run many of the studies for this disease and stay up to date on the latest research.

To find out how dermatologists diagnose and treat this type of eczema, go to: Nummular eczema: Treatment.

Used with permission of DermNZ

Bonamonte D, Foti C, et al. “Nummular eczema and contact allergy: a retrospective study.” Dermatitis. 2012;23(4):153-7.

Choi S, Zhu GA, et al. “Research letters: Dupilumab treatment of nummular dermatitis: A retrospective cohort study.” J Am Acad Dermatol. 2020;82(5):1252-5.

Jiamton S, Tangjaturonrusamee C, et al. “Clinical features and aggravating factors in nummular eczema in Thais.” Asian Pac J Allergy Immunol. 2013;31(1):36-42.

Lugović-Mihić L, Bukvić I, et al. “Factors contributing to the chronic urticaria/angioedema and nummular eczema resolution – Which factors are crucial?” Acta Clin Croat. 2019;58(4):595-603.

Miller JL, “Nummular dermatitis (nummular eczema).” In James WD [editor]. Medscape. Last updated November 2020.

Purnamawati S, Indrastuti N, et al. “The role of moisturizers in addressing various kinds of dermatitis: A review. Clin Med Res. 2017;15(3-4):75-87.

Written by:
Paula Ludmann, MS

Reviewed by:
Erin Ducharme, MD, FAAD
Amanda Friedrichs, MD, FAAD

Last updated: 3/15/21