Ten minutes into an intravenous antibiotic infusion, a client says their tongue feels thick and they are suddenly itchy. There is no rash yet. Blood pressure is normal. Some nurses would stop the infusion and page the provider. That is not enough, and the gap between those two responses is the whole subject of this lesson. Anaphylaxis is a rapid, systemic hypersensitivity reaction that can kill within minutes, and it kills in two ways at once: the upper airway swells shut, and the circulation collapses. What makes it so dangerous in practice is that the earliest findings are easy to attribute to something benign — anxiety, a mild allergy, a stuffy nose — and the definitive treatment is a medication that many clinicians hesitate over. There is very little to weigh here. Suspected anaphylaxis is treated immediately with intramuscular epinephrine into the outer thigh. Delay is the single most consistent factor in fatal cases. Antihistamines and corticosteroids have a role, but neither reverses airway swelling or circulatory collapse, and reaching for them first is one of the most dangerous substitutions...