Anaphylaxis

Anaphylaxis is a serious systemic hypersensitivity reaction that usually begins rapidly and can become life-threatening. Severe anaphylaxis can compromise the airway, breathing, or circulation and may cause death. Although hives, flushing, swelling, or other skin and mucosal symptoms are common, anaphylaxis can occur without them and does not always involve circulatory shock .^1,2

Anaphylaxis can affect several organ systems. Manifestations may include swelling of the upper airway, bronchospasm, difficulty breathing, low blood pressure, gastrointestinal symptoms, and skin or mucosal changes. The pattern and severity vary between reactions, so no single symptom is present in every case. Diagnosis is therefore based primarily on the clinical pattern and circumstances rather than on one definitive laboratory test .^1,2

Many episodes are caused by an IgE-mediated allergic mechanism. In a sensitized person, an allergen can cross-link IgE bound to high-affinity IgE receptors on mast cells and basophils, activating these cells and causing rapid release of mediators such as histamine and leukotrienes. These mediators can increase vascular permeability, alter vascular tone, and affect the airways and other tissues. However, pathways that do not depend on IgE can also produce anaphylaxis .¹

Anaphylaxis is therefore not synonymous with every allergic reaction. Allergic reactions vary widely in severity, whereas anaphylaxis refers to a systemic hypersensitivity reaction that can produce serious or life-threatening airway, breathing, or circulatory effects .^1,2