Nummular Eczema

The exact etiology of nummular eczema remains a subject of ongoing clinical research. However, it is widely accepted as a multifactorial condition involving skin barrier dysfunction and environmental triggers. Research published in the British Journal of Dermatology (2023) suggests that many patients have a localized deficiency in filaggrin—a protein essential for maintaining the skin's structural integrity. This deficiency leads to 'leaky' skin that is hypersensitive to external stimuli.

Non-Modifiable Risk Factors

• Age and Sex: As noted, older men and younger women are at higher risk.
• Genetics: A family history of atopy (asthma, hay fever, or atopic dermatitis) increases susceptibility.
• Skin Type: Individuals with naturally very dry skin (xerosis) are more prone to developing the condition.

Modifiable Risk Factors

• Environmental Dryness: Low humidity, particularly during winter months, is a major trigger.
• Skin Trauma: Injuries such as abrasions, insect bites, or chemical burns can trigger 'Koebnerization,' where eczema forms at the site of injury.
• Stress: High levels of psychological stress can exacerbate inflammatory responses in the skin.
• Medications: Certain drugs, such as interferon or isotretinoin, have been linked to the onset of nummular-like lesions.

Individuals living in cold, dry climates are at significantly higher risk. According to the National Eczema Association (2024), patients with pre-existing contact dermatitis—especially those sensitive to metals like nickel or chemicals like formaldehyde—show a higher incidence of nummular flares. Occupational exposure to skin irritants (e.g., cleaning agents, industrial chemicals) also increases risk.

While the underlying predisposition cannot always be changed, evidence-based prevention strategies focus on 'proactive skin barrier maintenance.' This includes:

• Consistent Emollient Use: Applying thick, fragrance-free moisturizers twice daily.
• Humidity Control: Using a humidifier in the home during winter.
• Irritant Avoidance: Switching to 'soap-free' cleansers and avoiding wool or synthetic fabrics directly against the skin.

The diagnostic journey typically begins with a primary care physician or a dermatologist. Diagnosis is primarily clinical, meaning it is based on the visual appearance of the lesions and the patient's medical history. Because nummular eczema can look identical to other conditions, a thorough evaluation is necessary to ensure the correct treatment path.

During the exam, the provider will inspect the shape, color, and distribution of the lesions. They will look for the characteristic 'coin' shape and check for signs of secondary infection, such as crusting or pustules. They will also ask about the severity of the itching and any known triggers.

• Skin Biopsy: If the diagnosis is uncertain, a small sample of skin tissue may be removed and examined under a microscope. This can help rule out psoriasis or cutaneous T-cell lymphoma.
• Patch Testing: This is often performed to determine if an undiagnosed contact allergy (e.g., to nickel or fragrances) is triggering the eczema.
• Skin Scrapings (KOH Test): A provider may scrape a small amount of scale from the lesion to look for fungal elements under a microscope, helping to rule out tinea corporis (ringworm).
• Bacterial Culture: If infection is suspected, a swab of the lesion fluid may be sent to a lab to identify the specific bacteria (usually Staphylococcus).

While there are no universal 'lab values' for nummular eczema, clinicians look for the presence of pruritic, coin-shaped, eczematous plaques that lack the central clearing typically seen in fungal infections and do not respond to standard antifungal treatments.

It is critical to distinguish nummular eczema from:

• Tinea Corporis (Ringworm): A fungal infection that usually has a clearer center.
• Psoriasis: Typically features thicker, silvery scales and different body distribution (knees/elbows).
• Contact Dermatitis: Inflammation caused by direct contact with an allergen.
• Stasis Dermatitis: Skin changes on the lower legs due to poor venous circulation.

The primary goals of treating nummular eczema are to reduce skin inflammation, alleviate the intense itching, and restore the skin's natural moisture barrier. Successful treatment is measured by the flattening of plaques, the cessation of weeping/oozing, and a significant reduction in the frequency of flares.

According to the American Academy of Dermatology (AAD) guidelines, the standard initial approach involves the aggressive use of high-potency topical corticosteroids and intensive moisturizing. This 'soak and smear' technique—applying medication to damp skin immediately after bathing—is highly effective for rapid symptom control.

• Topical Corticosteroids: These are the cornerstone of treatment. They work by suppressing the localized immune response and reducing swelling. Side effects of long-term use can include skin thinning (atrophy) or stretch marks.
• Topical Calcineurin Inhibitors (TCIs): These non-steroidal creams help modulate the immune system. They are often preferred for sensitive areas like the face or for long-term maintenance to avoid corticosteroid side effects. Common side effects include a temporary stinging sensation.
• Oral Antihistamines: While they do not treat the eczema itself, sedating antihistamines are often used at night to help patients sleep through the itching.
• Topical or Oral Antibiotics: If a secondary bacterial infection is present, a healthcare provider will prescribe a course of antibiotics to clear the infection, which often allows the eczema to heal more quickly.

• Phototherapy (Light Therapy): For patients who do not respond to topical treatments, controlled exposure to Narrowband Ultraviolet B (NB-UVB) light can reduce inflammation over several weeks.
• Systemic Immunomodulators: In severe, refractory (hard-to-treat) cases, oral medications that suppress the immune system globally may be considered.

• Wet Wrap Therapy: This involves applying topical medications and then covering the area with a layer of wet bandages followed by dry bandages. This increases medication absorption and provides a cooling effect that reduces itching.

Treatment typically lasts for several weeks until the skin is completely clear. Once the lesions have resolved, a maintenance routine of daily moisturizing is required to prevent recurrence. Regular follow-ups with a dermatologist are recommended for patients with chronic flares.

• Elderly Patients: Care must be taken with high-potency steroids due to naturally thinner skin.
• Pregnancy: Some systemic treatments are contraindicated, so topical management is prioritized.

> Important: Talk to your healthcare provider about which approach is right for you.

While nummular eczema is not typically caused by food allergies, some research suggests that a pro-inflammatory diet high in processed sugars may exacerbate skin inflammation. A 2023 study in Nutrients highlighted that a Mediterranean-style diet rich in Omega-3 fatty acids (found in fish and flaxseed) may support skin barrier health. Maintaining adequate hydration is also essential for skin moisture.

Exercise is beneficial for overall health, but sweat can be a major irritant for eczema plaques. Patients are encouraged to wear loose-fitting cotton clothing during exercise and to rinse off sweat immediately afterward using lukewarm water and a gentle cleanser.

Sleep hygiene is critical given the nocturnal nature of the itching. Keep the bedroom cool (around 65°F or 18°C), use 100% cotton bedding, and consider wearing cotton gloves at night to prevent skin damage from unconscious scratching.

Stress is a well-documented trigger for eczema flares. Evidence-based techniques such as mindfulness-based stress reduction (MBSR), deep breathing exercises, and progressive muscle relaxation have been shown to help lower systemic cortisol levels, potentially reducing the frequency of flares.

• Acupuncture: Some small-scale studies suggest it may help modulate the itch-scratch cycle, though more evidence is needed.
• Coconut Oil: When used as a moisturizer, virgin coconut oil has antimicrobial properties that may help prevent Staph colonization.
• Colloidal Oatmeal Baths: These can provide temporary relief from itching and help soothe inflamed skin.

Caregivers should help monitor the patient's skin for signs of infection and ensure the consistent application of moisturizers. For children or elderly patients, helping them avoid scratching by keeping fingernails short is a simple but effective intervention.

The prognosis for nummular eczema is generally good with appropriate medical management, though the condition tends to be chronic and prone to recurrence. According to clinical data from MedlinePlus (2023), most patients experience significant improvement within 4 to 6 weeks of starting a dedicated treatment regimen. However, the condition can persist for years if the underlying skin dryness and triggers are not addressed.

• Secondary Bacterial Infections: The most common complication, often caused by Staphylococcus aureus entering through scratched skin.
• Permanent Pigment Changes: Once a lesion heals, the area may remain darker (hyperpigmentation) or lighter (hypopigmentation) than the surrounding skin for several months.
• Lichen Simplex Chronicus: A condition where the skin becomes permanently thick and leathery due to chronic scratching.

Success depends on a 'barrier-first' mentality. This involves lifelong adherence to gentle skin care and the immediate treatment of new spots before they become large plaques. Annual or bi-annual check-ups with a dermatologist help ensure that the treatment plan remains effective.

Living well involves identifying personal triggers—such as specific soaps, cold weather, or stress—and having a 'flare-up kit' ready (prescribed creams and bandages). Joining support groups through organizations like the National Eczema Association can provide emotional support and practical tips.

Contact your healthcare provider if your current treatment plan is no longer controlling the itching, if new lesions appear rapidly, or if you notice signs of infection such as increased pain or pus.