Allergic contact dermatitis typically involves a reaction occurring how many hours after allergen exposure?

Allergic contact dermatitis is a type of delayed hypersensitivity reaction mediated by T cells, typically involving a response that manifests 24 to 72 hours after exposure to an allergen. This timing correlates with the primary immune response where sensitization takes place upon initial exposure; subsequent exposures trigger the immune system, leading to an inflammatory reaction.

In this context, the timeline of 24 to 72 hours allows enough time for the immune cells to recognize the allergen and orchestrate an inflammatory response. This range is essential for understanding the mechanism of allergic contact dermatitis and how it can be differentiated from other immediate hypersensitivity reactions, which manifest much sooner. Therefore, the answer accurately reflects the expected timing of symptoms associated with allergic contact dermatitis following allergen exposure.