Allergic and irritant contact dermatitis
Contact dermatitis is eczematous skin inflammation from an external agent, either irritant (direct, non-immune, the more common type) or allergic (a type IV delayed hypersensitivity). Diagnosis is clinical from the distribution and shape, with patch testing the gold standard to identify the allergen, and treatment is allergen or irritant avoidance plus topical corticosteroids.
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What this article covers
- Overview
Definition: contact dermatitis is eczematous inflammation of the skin caused by an external agent, occurring as irritant contact dermatitis (direct non-immune injury) or allergic contact dermatitis (a delayed type IV hypersensitivity).
- Epidemiology
Very common: among the most frequent dermatologic and occupational skin conditions.
- Risk factors
Repeated irritant exposure: frequent hand washing, wet work, solvents, and detergents (irritant type).
- Pathophysiology
Irritant contact dermatitis: direct chemical or physical damage to keratinocytes triggers innate inflammation without prior sensitization, so it can occur on first exposure and correlates with exposure intensity.
- Clinical features
Eczematous morphology: erythema, edema, vesicles, weeping, and later scaling and lichenification.
- Differential diagnosis
Atopic dermatitis: flexural, chronic, with a personal or family atopic history rather than a contactant pattern.
- Diagnosis
Diagnose clinically from the distribution and shape, and confirm the allergen with patch testing: contact dermatitis is a clinical diagnosis suggested by an eczematous eruption whose pattern matches…
- Management
First-line, identify and avoid the agent: remove the irritant or allergen, which is the definitive treatment; use barrier protection (gloves, emollients) for unavoidable exposures.
- Complications
Chronic hand dermatitis and lichenification: with fissuring and occupational disability.
- Prognosis
Excellent with avoidance: the dermatitis resolves once the agent is removed.
- Prevention
Avoid the identified allergen or irritant indefinitely, reading product labels for the specific agent.
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