What are the differences between irritant contact dermatitis and allergic contact dermatitis as described in the chapter?

Irritant contact dermatitis results from direct chemical injury to the skin, while allergic contact dermatitis is a type IV delayed hypersensitivity response that occurs in sensitized individuals. The former does not require prior exposure, whereas the latter necessitates sensitization to an antigen before a reaction occurs.

Irritant contact dermatitis is caused by direct damage to the skin from irritants, such as chemicals, and can occur upon first exposure. In contrast, allergic contact dermatitis involves a specific immune response to an allergen, requiring previous sensitization to develop. Symptoms of allergic contact dermatitis typically appear 2 to 7 days after exposure to the allergen, while irritant contact dermatitis may manifest more immediately after contact with the irritant.