What is the diagnosis and treatment for interface dermatitis?

Interface Dermatitis: Diagnosis and Treatment

Understanding Interface Dermatitis

Interface dermatitis is a histopathological pattern—not a single disease—characterized by inflammatory infiltrate obscuring the dermo-epidermal junction, basal cell vacuolization, and apoptotic keratinocytes (colloid/Civatte bodies). 1 This pattern encompasses multiple distinct clinical entities including lichen planus (most common at 63.2% of cases), lupus erythematosus, dermatomyositis, graft-versus-host disease, erythema multiforme, fixed drug eruptions, lichen striatus, and pityriasis lichenoides. 2, 1

The key diagnostic principle is that histopathology alone is insufficient—clinicopathologic correlation is absolutely essential for conclusive diagnosis, as the mere presence of interface changes should not be the sole criterion for diagnosis. 2

Diagnostic Approach

Clinical Assessment

• Document the morphology and distribution pattern: Look for papulosquamous lesions, erythematous plaques with visible borders, violaceous papules (lichen planus), photodistributed rash (lupus), or targetoid lesions (erythema multiforme). 2, 1
• Obtain detailed exposure history: Identify initial symptom location, spread pattern, relationship to specific products/activities, occupational exposures, and medication history (especially for fixed drug eruptions). 3
• Recognize that clinical features alone cannot reliably distinguish between different interface dermatitides or between irritant, allergic, and endogenous causes, particularly on hands and face. 4, 3

Histopathological Evaluation

Skin biopsy is essential for diagnosis, examining for: 1, 5

• Density, localization, and composition of inflammatory infiltrate
• Number and location of necrotic keratinocytes
• Epidermal changes (hyperplastic versus atrophic)
• Melanophages in papillary dermis
• Vacuolar alteration at the dermo-epidermal junction

Patch Testing When Indicated

For persistent or chronic dermatitis where allergic contact dermatitis is suspected, offer patch testing with an extended standard series of allergens. 4, 3 This is critical because:

• Clinical features are unreliable in distinguishing allergic from irritant contact dermatitis 4
• Defer testing 3 months after systemic agents and 6 months after biologics to minimize false negatives 4
• Avoid potent topical steroids on the back within 2 days of testing 3
• Keep prednisolone ≤10 mg daily if unavoidable during testing 3

Treatment Strategy

First-Line Management

The cornerstone of treatment is complete avoidance of identified causative agents combined with mid-to-high potency topical corticosteroids and aggressive emollient therapy. 3

Immediate interventions:

• Replace all soaps and detergents with emollients, as these are universal irritants that perpetuate inflammation regardless of the underlying cause 3
• Apply mid-to-high potency topical corticosteroids (e.g., triamcinolone 0.1% or clobetasol 0.05%) to affected areas 6, 3
• Use moisturizers packaged in tubes rather than jars to prevent contamination, applying two fingertip units after each hand washing 3
• Implement "soak and smear" technique: Soak affected areas in plain water for 20 minutes, then immediately apply moisturizer to damp skin nightly for up to 2 weeks 3

Protective Measures

Select appropriate gloves based on specific exposures:

• Rubber or PVC gloves with cotton liners for household tasks 3
• Neoprene or nitrile for latex allergy 3
• Thiuram-free gloves for rubber chemical allergy 3
• Check Material Safety Data Sheets for permeation times—no glove is completely impermeable 3

Remove gloves regularly to prevent sweat accumulation, which aggravates dermatitis. 3

Do not over-rely on barrier creams alone—they have questionable clinical value and may create false security, reducing implementation of appropriate preventive measures. 3 However, after-work creams have demonstrated benefit in reducing irritant contact dermatitis incidence. 3

Systemic Therapy for Extensive Disease

If allergic contact dermatitis involves >20% body surface area, systemic steroid therapy is required, offering relief within 12-24 hours. 6

For severe rhus dermatitis (poison ivy), taper oral prednisone over 2-3 weeks—rapid discontinuation causes rebound dermatitis. 6

Second-Line Therapies for Refractory Cases

When first-line treatment fails:

• Consider topical tacrolimus 0.1% where topical steroids are unsuitable, ineffective, or when chronic facial dermatitis raises concerns about steroid-induced skin damage (thinning, telangiectasia, perioral dermatitis). 3
• PUVA (psoralen plus UVA) phototherapy is an established second-line treatment for chronic hand eczema resistant to topical steroids, supported by prospective clinical trials. 3
• For severe chronic hand eczema specifically, offer alitretinoin (strong recommendation). 3
• Consider systemic immunosuppressants including methotrexate, mycophenolate mofetil, azathioprine, or ciclosporin for steroid-resistant chronic disease. 3

Occupational Interface Dermatitis

Arrange workplace visits to identify hidden allergens, assess procedures causing accidental exposure, and review Material Safety Data Sheets. 3

Implement comprehensive educational programs, which demonstrate improvements in established hand dermatitis and prevention of new cases. 3

Recognize the poor prognosis: Only 25% achieve complete healing over 10 years, 50% have intermittent symptoms, and 25% have permanent symptoms. 3 Changing occupation does not improve prognosis in 40% of cases. 3

Critical Pitfalls to Avoid

• Never diagnose based on histopathology alone—clinicopathologic correlation is mandatory 2
• Avoid washing with dish detergent, very hot/cold water, or disinfectant wipes 3
• Do not apply products containing topical antibiotics without indication 3
• Avoid prolonged occlusion without underlying moisturizer application 3
• Exercise extreme caution with topical corticosteroids on facial skin—prolonged use causes skin thinning, telangiectasia, perioral dermatitis, and red face syndrome due to increased percutaneous absorption 3
• Do not recommend exclusion diets—no good-quality studies support their use in interface dermatitis management 3

When to Escalate Care

Refer for dermatology consultation when:

• Diagnosis remains uncertain after initial evaluation and biopsy 2
• Treatment fails despite appropriate first-line therapy 3
• Patch testing is needed to identify specific allergens 4, 3
• Systemic immunosuppression is being considered 3
• Occupational dermatitis requires workplace assessment 3