Characteristics of Contact Dermatitis Rash
Contact dermatitis presents with a polymorphic rash characterized by erythema and vesiculation in the acute phase, and dryness, lichenification, and fissuring in the chronic phase. 1, 2
Types of Contact Dermatitis
Irritant Contact Dermatitis (ICD): More common form, caused by non-immune-mediated irritation of the skin by external substances 1, 2
- Acute ICD: Results from a single overwhelming exposure or few brief exposures to strong irritants or caustic agents 1, 2
- Chronic (cumulative) ICD: Occurs following repetitive exposure to weaker irritants such as detergents, solvents, soaps, weak acids/alkalis 1, 2
- Subjective irritancy: Idiosyncratic stinging reactions within minutes of contact, usually on the face, without visible changes 1, 3
Allergic Contact Dermatitis (ACD): Involves sensitization of the immune system to specific allergens, carries worse prognosis unless allergen is identified and avoided 1, 2
Other types: Phototoxic/photoallergic contact dermatitis (triggered by light exposure), systemic contact dermatitis, and protein contact dermatitis 1, 2
Clinical Presentation
Acute Phase Characteristics
- Well-demarcated erythematous lesions with visible borders 4
- Vesicles and bullae in dramatic flares 4
- Pruritus (more common in allergic contact dermatitis) 5
- Stinging and burning sensations (more common in irritant contact dermatitis) 5
- Edema may be present 4, 6
Chronic Phase Characteristics
- Dryness and scaling 1, 4
- Lichenification (thickening of skin with accentuated skin markings) 1, 7
- Fissuring and cracking of the skin 1, 4
- Hyperkeratosis 7, 8
Distribution and Patterns
- Lesions are primarily confined to the site of contact with the offending agent 7
- Hand dermatitis is common (point prevalence of 2%, lifetime risk of 20%) 1
- Facial dermatitis often presents with subjective irritancy without visible changes 3
- Pattern and morphology alone are unreliable in distinguishing between different types of dermatitis 1, 3
Key Diagnostic Features
- Well-demarcated borders in irritant contact dermatitis compared to allergic forms 5
- Irritant contact dermatitis patients report more stinging and burning than itching 5
- Allergic contact dermatitis patients report more pruritus 5
- Clinical features alone are unreliable in distinguishing allergic contact from irritant and endogenous dermatitis 1, 2
Common Pitfalls in Diagnosis
- Misdiagnosis between different types of dermatitis is common due to similar clinical presentations 3
- The pattern and morphology of dermatitis, particularly on hands and face, is unreliable in predicting cause 1, 3
- Contact dermatitis can mimic many skin diseases including atopic dermatitis and lichen planus 8
- Multiple subtypes may occur simultaneously, complicating diagnosis 6
Important Considerations
- Contact dermatitis accounts for 4-7% of dermatological consultations 1
- Occupational factors play a significant role, with contact dermatitis making up approximately 70% of occupational skin disease 2
- Common allergens include nickel (14.5%), fragrance compounds (37%), cobalt (22%), and p-phenylenediamine (1%) 1, 2
- Patch testing is essential for confirming allergic contact dermatitis when suspected 1, 3