Reactive Dermatitis • ICD-11: EK00

Contact Dermatitis: Irritant vs. Allergic (Type IV Hypersensitivity) & Patch Testing Standards

Author: Mallikarjun R (Founder) & Medicus Labs Medical Team • Review: 11 min read • ✓ Peer-Referenced

1. Irritant vs. Allergic Contact Dermatitis

Contact Dermatitis encompasses Irritant Contact Dermatitis (80% of cases; non-immunological direct chemical/physical disruption of keratinocytes) and Allergic Contact Dermatitis (20% of cases; Type IV delayed cell-mediated hypersensitivity triggered by haptens like nickel, fragrances, and preservatives).

2. Clinical Diagnostic Patch Testing

Epicutaneous patch testing (read at 48 and 96 hours) identifies specific hapten sensitivities. Management requires strict allergen avoidance, topical corticosteroids during acute vesicular flares, and barrier lipid replacement.