What is the typical presentation and treatment of contact dermatitis in adults and children?

Contact Dermatitis: Clinical Presentation and Pattern Recognition

Distinguishing Clinical Features

Contact dermatitis presents with two distinct temporal patterns: acute disease shows erythema and vesiculation with pruritus, while chronic disease manifests as dryness, lichenification, and fissuring with visible borders. 1

Acute Phase Characteristics

• Erythema (redness) at sites of contact with clearly demarcated borders 1, 2
• Vesiculation that can progress to blister or bullae formation 1, 3
• Intense pruritus (itching) is prominent 1, 2
• Weeping and oozing may occur in severe cases 3

Chronic Phase Characteristics

• Marked dryness with scaling develops from repeated exposure 1
• Lichenification (skin thickening) occurs due to chronic scratching 1, 2
• Fissures appear, especially in areas of flexion or movement 1
• Erythematous lichenified plaques replace acute vesicular changes 3

Two Distinct Pathophysiologic Types

Irritant Contact Dermatitis

Irritant contact dermatitis results from direct chemical damage to the skin without immune system involvement, causing inflammation through release of mediators from damaged epidermal cells. 4

• Affects all individuals in a dose-dependent manner (no prior sensitization required) 4
• Caused by acids, alkalis, soaps, detergents, and prolonged water exposure 4
• Results in erythema, edema, scaling, itch, and occasional pain 4
• More common than allergic contact dermatitis but generally has better prognosis if irritant is removed 5
• Can be acute (single overwhelming exposure) or chronic/cumulative (repetitive exposure to weaker irritants) 5

Allergic Contact Dermatitis

Allergic contact dermatitis occurs only in susceptible individuals through a delayed hypersensitivity (Type IV) reaction requiring prior sensitization to specific antigens. 4, 2

• Requires prior sensitization followed by re-exposure to trigger reaction 4, 2
• Common allergens include nickel (affects ~10% of women with pierced ears), neomycin (5-15% of chronic otitis patients), fragrances, metals, cosmetics, and topical medications 4, 5
• Even minute exposures can trigger rash in sensitized individuals 6
• Carries worse prognosis than irritant dermatitis unless allergen is identified and avoided 5
• A maculopapular and often eczematous eruption on exposed areas is consistent with allergic reaction 4

Distribution Patterns Provide Diagnostic Clues

Location-Specific Patterns

• Ear canal: Erythematous streak may extend down the pinna where drops contact auricular skin 4
• Airborne allergen exposure: Face, neck, arms, legs, and "V" area of chest more severely affected 1
• Occupational exposure: Clearly demarcated areas at sites of workplace contact with oils, grease, or chemicals 6
• Hand dermatitis: Point prevalence ~2%, lifetime risk 20%, accounts for ~70% of occupational skin disease 5

Critical Diagnostic Limitation

Clinical features alone are unreliable for distinguishing allergic from irritant or endogenous eczema, particularly with hand and facial involvement. 5, 1

• Pattern and morphology cannot reliably predict cause 5
• Patch testing is essential for confirming allergic contact dermatitis (sensitivity and specificity 70-80%) 5
• Patch testing should be performed when allergic contact dermatitis is suspected or cannot be ruled out 5

Treatment Approach

First-Line Management for Adults

• Mid- to high-potency topical corticosteroids (triamcinolone 0.1% or clobetasol 0.05%) for localized acute lesions 2
• Systemic corticosteroids (oral prednisone tapered over 2-3 weeks) for extensive involvement (>20% body surface area) to prevent rebound dermatitis 2
• Topical calcineurin inhibitors (tacrolimus 0.1% ointment or pimecrolimus 1% cream) for facial/intertriginous areas to avoid steroid atrophy 4, 7
• Liberal emollient application to restore barrier function 4, 8

Pediatric-Specific Considerations

For children, use low to medium potency topical corticosteroids as first-line therapy, applied once to twice daily for 1-2 weeks, with potency selection based on age, body site, and severity. 8

• Ages 0-6 years require lower potency due to high body surface area-to-volume ratio increasing HPA axis suppression risk 8
• Never use ultra-high-potency corticosteroids on face, neck, or skin folds due to atrophy risk 8
• Topical calcineurin inhibitors (tacrolimus 0.03% or pimecrolimus 1%) preferred for facial/intertriginous areas in children ≥2 years 8, 7
• Common pediatric allergens include nickel, topical antibiotics, preservatives, fragrances, and rubber accelerators 8

Essential Adjunctive Measures

• Allergen/irritant avoidance is the cornerstone of management once identified 8
• Oral antihistamines for pruritus control, particularly at bedtime 8, 9
• Cold water compresses for symptomatic relief 9
• Replacement of soaps/detergents with emollients 4

Critical Pitfalls to Avoid

• Do not rely on clinical appearance alone to distinguish allergic from irritant dermatitis—patch testing is required 5, 1
• Avoid topical antibiotics routinely as they increase resistance and sensitization risk (neomycin sensitizes 5-15% of patients) 4, 8
• Do not use barrier creams as primary protection—they provide false security and questionable value 8
• Avoid rapid steroid discontinuation in severe cases—taper over 2-3 weeks to prevent rebound 2
• Do not overlook allergen identification—only 25% of occupational contact dermatitis cases achieve complete healing, with 50% having intermittent symptoms at 10 years 4, 8

Environmental Exacerbating Factors

• Hot water (>40°C) damages skin barrier through lipid fluidization and increased permeability 5
• Cold or very cold water for handwashing is a specific risk factor 5
• Low relative humidity compounds irritation 5
• More frequent handwashing (cold/flu season) without adequate barrier restoration worsens disease 5