Approach Considerations
Hydration of the skin is the most important factor in treating nummular eczema. Use of hypoallergenic, fragrance-free creams, lotions, or ointments is the first step in therapy.
Medical Care
Treatment is aimed at rehydration of the skin, repair of the epidermal lipid barrier, reduction of inflammation and treatment of any infection. Medications and emollients are best absorbed by dampening the skin first.
Lukewarm or cool baths or showers reduce itching and help rehydrate the skin; a gentle soap or liquid cleanser may be used. Skin should be patted dry and then moisturizers are applied to still-damp skin. The "soak-and-smear" therapeutic regimen includes a 20-minute plain water soak each night followed by application of steroid ointment or petrolatum to wet skin and includes alteration of cleansing habits so that soap is applied only to the axilla and groin. One study showed greater than 90% response in 27 of 28 patients with refractory chronic pruritic eruptions when the regimen was followed as directed. [32]
Wet wrap treatments are often helpful. This involves dampening the skin with lukewarm water until it is well hydrated (usually 10 min). Then, petrolatum or steroid ointment is applied liberally, followed by occlusion for 1 hour with damp pajamas or a nonbreathable sauna suit. For small areas of involvement, plastic wrap may be used to occlude the area. This process may be repeated 5-6 times a day with petrolatum. Caution must be used when prescription steroid medications are used because overuse of these medications can cause striae, thinning of the skin, and, rarely, enough systemic absorption of steroid to affect the hypothalamic-pituitary-adrenal axis.
Steroids are the most commonly used therapy to reduce inflammation. Less erythematous, less pruritic lesions may be treated with low-potency (class III-VI) steroids. Severely inflamed lesions with intense erythema, vesicles, and pruritus require high-potency (class I-II) preparations. Penetration of the medication is enhanced by occlusion and/or presoaking in a tub of plain water followed immediately (without drying) by application of the steroid-containing ointment.
Ointments are usually more effective than creams because they are more occlusive, form a barrier between the skin and the environment, and more effectively hold water into the skin. However, patients may be more likely to use a cream formulation; education and discussion is key to patient compliance.
Oral, intramuscular, or parenteral steroids may be required in cases of severe, generalized eruptions.
Tar preparations are helpful to decrease inflammation, particularly in older, thickened, scaly plaques.
Topical immune modulators (tacrolimus and pimecrolimus) also reduce inflammation. [33] These are often initiated a few days after the topical steroid to decrease the risk of a burning sensation that may occur when applied to extremely irritated skin. Other topical treatments that are currently approved for atopic dermatitis may be helpful, including crisaborole and topical ruxolitanib, though data specifically for nummular eczema is lacking.
When eruptions are generalized and prolonged, more aggressive therapy is warranted. Systemic steroids have long been a mainstay for the treatment of dermatitis, including nummular eczema, though it ahould only be used with short courses and when topical treatmetn has been insufficient. Cyclosporine A has been used as an alternative to systemic steroids, though requires monitoring of blood pressure and renal function. Phototherapy (generally with ultraviolet [UV] B) may be helpful. [34] Broadband or narrowband UVB is most commonly used, although psoralen plus UVA (PUVA) may be used in severe cases. Oral immunosuppressive agents may help to attenuate the immune response; methotrexate has been used successfully in children with nummular eczema. [35] Data are lacking for other immunosuppressants such as azathioprine and mycophenolate mofetil in the treatment of nummular eczema, although these medications have been used in other forms if dermatitis. Dupilumab, a monoclonal antibody targeting interleukins 4 and 13, has also been used successfully to treat nummular eczema [36] . Treatment with inhibitors of JAK kinase has not been reported, but given success in atopic dermatitis these medications may develop a role in treating extremely refractory cases of nummular eczema.
Mindfulness-based therapies, including meditation and hypnotherapy, have also been reported to be helpful. [37]
Oral antihistamines or sedatives may help reduce itching and improve sleep. Topical antihistamines are known to be potent topical sensitizers, and, thus, preparations containing topical diphenhydramine in particular should not be used. Oral gabapentin and pregabalin as well as opioid receptor antagonists may be more efficacious in treating itching due to nummular eczema. [38]
Topical antibiotics such as mupirocin may help impetiginization; as neomycin- or bacitracin-containing medications are potent topical sensitizers, these should be avoided.
Oral antibiotics, such as dicloxacillin, cephalexin, or erythromycin, should be used in cases of secondary infection. Swab cultures of the skin guide selection of antibiotics.
Once the eruption has resolved, ongoing aggressive hydration may decrease the frequency between flares, particularly in dry climates. Heavy moisturizers (preferably a sensitive-skin formulation) or petroleum jelly applied to damp skin after showering may be helpful.
Disease may be severe and refractory to the above treatments. Immune-suppressive medications such as methotrexate have been described to be safe and effective in these severely affected patients. [39, 35]
Consultations
Because lesions are persistent and may be difficult to treat, consultation with a dermatologist in an outpatient setting may be advisable.
Activity
Activities that heat or dry the skin worsen the pruritus and the eruption. Resting in a cool, moist environment is therapeutic. Heat, soap, drying conditions, and irritating activities should be avoided. Extreme cold may also exacerbate nummular eczema.
Sunlight or phototherapy may be beneficial, particularly in chronic cases. Ultraviolet radiation helps reduce the inflammatory activity within the skin. The risk of heat worsening the pruritus and of ultraviolet light inducing cutaneus malignancies must be weighed against the potential benefits.
Prevention
Aggressive hydration of the skin may decrease the frequency between nummular dermatitis eruptions.
Bathing is permissible, but hot water should be avoided. Patients should use mild, nondrying cleansers. Patients should be encouraged to use nonsoap cleansers only for control of body odor and cleanliness (eg, on the groin, axillae, and feet). Oil additives may be used in bathing water. To avoid drying of the lesions, an emollient should be used immediately after bathing. The skin may be patted and the emollient applied before the skin is completely dry. Clothing should be loose to avoid overheating, and irritating fibers, such as wool, should be avoided.
A room humidifier is useful, particularly when a heater or air conditioning is used.
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Dry, scaling plaque of nummular dermatitis (size, 3 X 5 cm) on the shin.
