Anaphylaxis is the most severe form of allergic reaction, driven by massive mast cell and basophil degranulation releasing histamine, prostaglandins, and leukotrienes. This causes simultaneous airway oedema, bronchospasm, and vascular collapse — a combination that can be fatal within minutes without immediate epinephrine administration. Epinephrine is the only first-line treatment for anaphylaxis — it reverses bronchospasm, reduces mucosal oedema, and maintains circulation. Antihistamines and corticosteroids are important adjuncts but are too slow-acting to treat the acute emergency. All patients with anaphylaxis should be observed in hospital for at least 4–6 hours due to the risk of biphasic reaction.
