Nummular Eczema: Symptoms, Types, Causes and Treatment

Nummular eczema, also known as discoid eczema or nummular dermatitis, is a unique and sometimes misunderstood skin condition. Unlike other forms of eczema, nummular eczema is characterized by its distinctive coin-shaped patches, often causing confusion with other skin diseases such as ringworm or psoriasis. Understanding its symptoms, types, causes, and available treatments is key to effective management and improved quality of life for those affected. This article provides a comprehensive, evidence-based overview of nummular eczema, drawing on up-to-date scientific research and clinical expertise.

Symptoms of Nummular Eczema

Nummular eczema stands out for its characteristic appearance and the discomfort it causes. Recognizing the signs and understanding their impact is crucial for prompt diagnosis and management.

Symptom	Description	Location	Source(s)
Pruritus	Intense itching, often the most distressing symptom	Lesion sites	1, 2, 9
Coin-shaped Lesions	Sharply defined, round or oval, erythematous plaques	Extremities (legs, arms), hands, trunk	1, 2, 5
Oozing/Crusting	Yellowish exudate, crust formation on lesions	Lesion sites	1, 4, 5
Dry Skin	Generalized or localized dryness, often preceding lesions	Surrounding skin	1, 2, 9
Vesicles and Papulovesicles	Small fluid-filled bumps on plaques	Lesion sites	5
Symmetrical Distribution	Lesions commonly appear on both sides of body	Limbs	2, 5, 9

Table 1: Key Symptoms

Overview of Symptoms

Nummular eczema creates a significant impact on daily life, predominantly due to the intense itching (pruritus) and visible skin changes. The coin-shaped, sharply demarcated lesions are the hallmark of this condition, ranging from 1 to 10 cm in diameter and often accompanied by oozing and crusting, especially during acute flares 1, 2, 4, 5. These plaques frequently arise on the legs and arms but can develop anywhere, including the trunk and hands 1, 2, 5, 9.

Typical Lesion Appearance

• Shape & Size: Lesions are typically round or oval, with a well-defined edge. They may grow by merging with smaller nearby patches or by expansion of the original site 2, 5.
• Surface Features: In the acute phase, the plaques may weep (ooze) and form yellowish crusts. Over time, they can become dry and scaly. Dermoscopy can reveal shiny yellow clods, a distinguishing feature from similar skin conditions 4.
• Associated Findings: Small vesicles and papulovesicles are often seen within the plaques, especially in new or inflamed lesions 5.

Distribution and Impact

• Common Sites: Most frequently, nummular eczema affects the lower limbs, followed by upper limbs, hands, and sometimes the trunk 2, 5, 9.
• Symmetry: Lesions can be multiple and often appear symmetrically.
• Quality of Life: The itching and visible plaques can significantly impair quality of life, especially in younger individuals and those with widespread or trunk involvement 9.

Additional Features

• Dry Surrounding Skin: Dryness typically precedes lesion development and is present in most patients, aggravating the condition 1, 2, 9.
• Misdiagnosis Risk: Due to their annular (ring-shaped) appearance, nummular eczema lesions are sometimes misdiagnosed as ringworm (tinea corporis) or psoriasis 1, 2, 4.

Types of Nummular Eczema

While nummular eczema is generally characterized by its coin-shaped lesions, variations exist based on age, underlying conditions, and associated features. Recognizing these types can guide personalized treatment and prognosis.

Type	Distinct Features	Age Group / Association	Source(s)
Classical Nummular Eczema	Typical coin-shaped plaques, pruritus	Adults (esp. middle-aged, elderly)	1, 2, 5, 9
Nummular Atopic Dermatitis	Coin-shaped lesions with atopic features	Children, those with atopy	6, 3, 13
Microbial/Exudative NE	Sharply demarcated, serous exudate, yellow clods	Elderly, immunocompromised	4, 7
Refractory/Severe NE	Persistent, widespread, resistant to standard therapy	Any (often with underlying triggers/allergies)	12, 15, 11

Table 2: Types of Nummular Eczema

Classical Nummular Eczema

This is the most common presentation, especially in adults and the elderly. Lesions are well-circumscribed, coin-shaped plaques with variable oozing, scaling, and crusting 1, 2, 5. Men tend to develop it later in life, while women are more likely to be affected at a younger age 1.

Nummular Atopic Dermatitis

Some patients, particularly children, display a nummular pattern as a variant of atopic dermatitis (AD). These patients may have a personal or family history of allergies or atopic disease. Studies show overlapping molecular signatures between nummular eczema and classical AD, with both showing impaired skin barriers and immune dysregulation 3, 6, 13. Nummular atopic dermatitis is sometimes more variable in location and can be associated with more severe keratosis pilaris in children 6.

Microbial/Exudative Nummular Eczema

Certain cases, especially in the elderly or immunocompromised, may present with prominent exudation and secondary infection. Dermoscopically, these can show multiple yellow clods, which are not typical in psoriasis or tinea corporis 4. This form is often linked to skin barrier dysfunction and increased susceptibility to environmental or microbial allergens 7.

Refractory or Severe Nummular Eczema

Some patients experience chronic, widespread, or treatment-resistant disease. These cases may be associated with underlying contact allergies, dental infections, or other systemic factors 11, 12, 15. Children with severe, persistent disease may require advanced therapies such as methotrexate 12, 15.

Causes of Nummular Eczema

The exact cause of nummular eczema is still not fully understood, but research has identified several factors that may contribute to its development and flare-ups.

Cause	Mechanism/Association	Population Most Affected	Source(s)
Skin Barrier Dysfunction	Dry skin, increased transepidermal water loss, impaired lipid layers	Elderly, atopic individuals	1, 3, 6, 7
Contact Allergens	Nickel, cobalt, potassium dichromate, house dust, others	Adults with persistent NE	8, 9, 10
Atopy & Immune Reactivity	Delayed hypersensitivity, co-dominant Th2/Th17 response	Children, atopic adults	3, 6, 7, 9
Environmental Triggers	Cold/dry weather, hot baths, harsh soaps, emotional stress	All ages, esp. elderly	2, 7, 9
Secondary Infections	Bacterial colonization, dental infections	Severe/refractory cases	1, 11

Table 3: Causes and Aggravating Factors

Skin Barrier Dysfunction

A central theme in nummular eczema is the breakdown of the skin’s protective barrier. Studies reveal that affected individuals have reduced hydration, increased water loss, and disruption of the intercellular lipid lamellae, making the skin more permeable to irritants and allergens 1, 6, 7. This is particularly pronounced in the elderly, whose skin tends to be drier and more vulnerable 7.

Allergens and Irritants

Contact allergy is a well-established contributor to nummular eczema. Patch testing has found a high prevalence of sensitization to metals (nickel, cobalt, potassium dichromate), fragrances, and environmental allergens like house dust mites 8, 9. Persistent or treatment-resistant lesions should prompt investigation for hidden allergens 8, 10.

Atopy and Immune Response

Nummular eczema frequently occurs in individuals with a personal or family history of atopy (e.g., asthma, hay fever, classical eczema) 3, 6, 9. The immune profile of nummular eczema often overlaps with atopic dermatitis, featuring both type 2 (Th2) and type 3 (Th17) immune responses 3.

Environmental and Lifestyle Triggers

Environmental factors such as cold, dry weather, excessive bathing with hot water, and the use of harsh soaps can exacerbate the skin’s dryness and trigger flare-ups 2, 7, 9. Emotional stress and alcohol consumption have also been identified as aggravating factors 9.

Secondary Infections

Bacterial colonization, particularly by Staphylococcus aureus, can worsen the condition. In some cases, hidden sources of infection, such as dental or implant-related infections, have been linked to recalcitrant nummular eczema, with improvement seen after treating the underlying infection 1, 11.

Treatment of Nummular Eczema

Effective management of nummular eczema requires a multifaceted approach—addressing both the underlying causes and the immediate symptoms. Treatment strategies are tailored to disease severity, patient age, and response to previous therapies.

Treatment Approach	Key Elements / Medications	Indications / Notes	Source(s)
Skin Care & Moisturizers	Regular emollients, avoid hot baths/harsh soaps	All patients; prevent recurrences	1, 2, 7, 9
Topical Corticosteroids	High or ultra-high potency steroids	First-line for acute flares	1, 2, 5, 15
Topical Calcineurin Inhibitors	Tacrolimus, pimecrolimus	Alternative to steroids; sensitive areas	2, 13
Systemic Therapies	Methotrexate, oral antibiotics, dupilumab	Severe/refractory cases	12, 13, 15
Allergen Avoidance	Patch testing, removal of triggers	Chronic/persistent disease	8, 9
Treat Infections	Oral antibiotics, manage dental/implant sources	Oozing, crusted, or recalcitrant lesions	1, 11
Other Therapies	Phototherapy, Korean medicine, stress reduction	Adjuncts or alternative options	14, 9

Table 4: Treatment Strategies

Skin Care and Moisturization

Maintaining skin hydration is the foundation of nummular eczema management. Patients should be advised to use fragrance-free emollients multiple times daily, avoid prolonged hot showers or baths, and steer clear of harsh soaps or detergents 1, 2, 7, 9. These measures reduce flare frequency and support skin barrier repair.

Topical Therapies

• Corticosteroids: High or ultra-high potency topical steroids are the mainstay for acute lesions. They rapidly reduce inflammation and itching 1, 2, 5, 15.
• Calcineurin Inhibitors: In sensitive skin areas or for long-term management, topical tacrolimus or pimecrolimus can be considered 2, 13.

Systemic and Advanced Therapies

• Methotrexate: For moderate to severe cases, especially in children unresponsive to topical treatments, low-dose methotrexate has been shown to induce remission safely 12, 15.
• Dupilumab: This biologic agent targeting interleukin-4 and -13 has demonstrated efficacy in adults with nummular eczema as a phenotype of atopic dermatitis 13.
• Oral Antibiotics: Used for secondary bacterial infection or extensive weeping lesions 1.

Identifying and Avoiding Triggers

Patch testing is crucial for patients with chronic or relapsing disease to identify and avoid specific allergens 8, 9. This can include metals, fragrances, house dust mites, and others.

Managing Infections

Treatment of underlying infections, including dental or implanted medical device sources, is important for refractory cases 1, 11.

Adjunct and Alternative Therapies

• Phototherapy: May be considered for widespread or treatment-resistant disease 2.
• Korean Medicine and Herbal Treatments: Some studies suggest benefit, though high-quality evidence is limited 14.
• Lifestyle Adjustments: Stress management, alcohol moderation, and gentle skin care are all recommended 9.

Conclusion

Nummular eczema is a complex, chronic skin disorder that can significantly impact quality of life. Understanding its unique symptoms, types, underlying causes, and evidence-based treatment options is essential for effective management.

Key takeaways:

• Nummular eczema presents as intensely itchy, coin-shaped lesions, most often on the limbs but potentially affecting other sites 1, 2, 5, 9.
• Subtypes include classical, atopic, exudative/microbial, and refractory forms, each with distinct features and associations 3, 4, 6, 13.
• The main drivers are skin barrier dysfunction, contact allergies, atopic tendencies, environmental factors, and sometimes secondary infections 1, 3, 6, 7, 8, 9, 11.
• Management focuses on optimal skin care, potent topical corticosteroids, identification and avoidance of allergens, and, in severe cases, systemic therapies such as methotrexate or dupilumab 1, 2, 12, 13, 15.
• Supportive care, education, and attention to quality of life are vital for long-term success.

With proper diagnosis and a personalized, holistic approach, most patients with nummular eczema can achieve good control of their symptoms and minimize disease impact.