Contact Dermatitis: Differentiating Irritant and Allergic Mechanisms

Contact dermatitis (CD) is a highly prevalent inflammatory skin disorder caused by exposure to exogenous substances. It encompasses two principal subtypes: irritant contact dermatitis (ICD), a non–immune-mediated condition resulting from direct cytotoxic injury, and allergic contact dermatitis (ACD), a T cell–mediated delayed hypersensitivity reaction. ICD accounts for the majority of cases and results from direct cytotoxic effects on keratinocytes, whereas ACD requires prior sensitization and exhibits a delayed clinical onset. Differentiating between these entities is essential for accurate diagnosis, appropriate management, and long-term prevention strategies. This review provides a detailed analysis of the molecular mechanisms, clinical features, diagnostic strategies, and therapeutic approaches of ICD and ACD.