Anaphylaxis is a severe, life-threatening, generalized or systemic hypersensitivity reaction. The most common mechanism is Type I hypersensitivity, which is IgE-mediated. Upon re-exposure to an allergen, specific IgE antibodies bound to mast cells and basophils trigger the rapid release of potent vasoactive and bronchoactive mediators like histamine, tryptase, leukotrienes, and prostaglandins. These mediators lead to widespread vasodilation, increased vascular permeability, and bronchoconstriction. While non-IgE mediated (anaphylactoid) reactions can also occur, the clinical presentation and initial management are similar.
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