Unit
- Definition: Contact dermatitis is an inflammatory skin reaction caused by direct contact with an external substance. It manifests as erythema, pruritus, and vesiculation at the site of exposure.
- Irritant contact dermatitis (ICD): Accounts for 80% of cases. Caused by direct damage to the skin barrier from chemicals, solvents, or physical agents. Severity depends on concentration and duration.
- Allergic contact dermatitis (ACD): A delayed-type hypersensitivity reaction (Type IV). Requires prior sensitization. Common allergens include nickel, fragrances, and preservatives.
- Phototoxic and photoallergic: Reactions triggered by sunlight exposure after contact with certain chemicals. Phototoxic is non-immunologic; photoallergic involves immune response.
- Acute vs chronic presentation: Acute shows weeping vesicles and erythema; chronic presents with scaling, fissuring, and lichenification from repeated exposure.
- Prevalence and impact: Affects 15-20% of the general population. Occupational contact dermatitis is among the most common work-related diseases, causing significant lost productivity.
- Economic burden: Direct medical costs include dermatology visits, patch testing, and medications. Indirect costs from absenteeism and disability claims add substantial financial strain.
- Course objectives: This module establishes foundational knowledge to differentiate ICD from ACD, recognize common triggers, and appreciate the public health importance of management.
- Pathophysiology of ICD: Direct cytotoxic damage to keratinocytes triggers the release of pro-inflammatory cytokines such as IL-1 alpha and TNF-alpha. This non-specific innate immune response leads to vasodilation and neutrophil recruitment without requiring prior sensitization. The severity correlates directly with the concentration and duration of exposure to the offending agent.
- Pathophysiology of ACD: Small reactive chemicals called haptens penetrate the skin and bind to carrier proteins. Langerhans cells process this complex and migrate to draining lymph nodes to present the antigen to naive T cells, initiating sensitization. Upon re-exposure, memory T cells rapidly orchestrate a delayed hypersensitivity reaction.
- Common ICD triggers: Frequent exposure to water and soaps causes irritant dermatitis in healthcare workers and homemakers. Solvents, degreasers, and cutting fluids strip protective lipids from the stratum corneum. Strong acids and bases cause direct tissue necrosis and a more severe acute irritant reaction.
- Diagnostic approach: A meticulous history focusing on temporal relationships between exposures and flares is critical. The anatomic distribution often points to the cause, such as earlobe involvement suggesting nickel or hand dermatitis suggesting occupational or wet work exposure. Patch testing remains the gold standard for confirming allergic contact dermatitis.
- Management strategies: Strict avoidance of confirmed triggers is the cornerstone of therapy. Protective barriers like nitrile gloves and barrier creams can mitigate exposure in occupational settings. Treatment of active lesions includes topical corticosteroids, wet dressings for acute oozing, and systemic steroids for severe widespread reactions.
- Prognosis and prevention: Irritant contact dermatitis often resolves quickly if the offending agent is removed and the skin barrier is repaired. Allergic contact dermatitis involves lifelong sensitization, but diligent avoidance leads to clearance over weeks. Primary prevention focuses on workplace safety protocols and patient education to minimize future exposures.
Scope of Practice
Role: Dermatology Clinic Coordinator
Within scope:
- Scheduling initial consultations for suspected contact dermatitis.
- Educating patients on basic skin care and avoidance of irritants.
- Coordinating patch testing appointments and preparing materials.
- Documenting patient history of exposures and symptoms.
- Referring complex cases to dermatologists for diagnosis.
Outside scope:
- Interpreting patch test results independently.
- Prescribing topical corticosteroids or systemic treatments.
- Diagnosing the specific type of contact dermatitis.
- Performing skin biopsies or other invasive procedures.
- Advising on allergy immunotherapy for contact allergens.
Quick Revision
- Contact dermatitis is an inflammatory skin reaction to external substances.
- Irritant contact dermatitis results from direct skin barrier damage.
- Allergic contact dermatitis is a delayed hypersensitivity reaction.
- Acute vs chronic presentations differ in signs and symptoms.
- Prevalence is high, with significant economic impact.