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Nummular dermatitis: Causes


Who gets nummular dermatitis?

This skin problem is more common in men than in women. Men tend to have their first outbreak between 55 and 65 years of age. Women are more likely to get it between the ages of 15 and 25 years. It is rare in children.

Nummular dermatitis blisters

Nummular dermatitis blisters can form and grow together to create red patches.

What causes nummular dermatitis?

While the cause is unknown, researchers think that sensitivity plays a role in some cases. A person may be sensitive to: 

  • Metals, including nickel and rarely mercury, such as from dental fillings.

  • Formaldehyde.

  • Medicines, such as neomycin (an antibiotic that you apply to the skin).

If the person has a sensitivity to something, the skin will only clear when the person avoids that substance. 

Research also suggests that your risk of getting nummular dermatitis increases if you live in a cold, dry climate or have: 

  • Very dry skin (xerosis).

  • Another type of eczema, mainly atopic dermatitis or stasis dermatitis. 

  • Poor blood flow and/or swelling in the legs.

  • Injured your skin (insect bite, contact with chemicals, or abrasion).

  • A skin infection caused by bacteria.

  • Taken certain medicines, such as isotretinoin and interferon. Isotretinoin, a prescription medicine sometimes used to treat severe acne, seems to increase the risk for this skin problem. Interferon can cause severe widespread nummular dermatitis.


All content solely developed by the American Academy of Dermatology

Supported in part by: Leo-fnl

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