Allergic and hypersensitivity reactions in the intensive care unit

Hypersensitivity reactions are defined as immunologically based adverse reactions to chemicals or medicinal agents. These reactions are common in the intensive care unit and can present as a simple, mildly symptomatic rash or as life-threatening anaphylactic reactions. Hypersensitivity reactions have traditionally been classified as types I to IV reactions based on the underlying immune mechanisms, although the clinical relevance of the classification is unclear, and new subtypes to this system have been recently proposed. Given the immunologic and often unpredictable nature of these reactions, avoidance or prevention is not a feasible option. Therefore, management has primarily consisted of withdrawal of potential offending agents, supportive therapy, symptomatic management, and, in some specific examples, targeted pharmacotherapy. This article outlines the background and types of hypersensitivity reactions and provides descriptions and management strategies when applicable to common types of hypersensitivity reactions encountered in the intensive care unit.