A 34-year-old woman presents to the Emergency Department 10 minutes after receiving intravenous co-amoxiclav in an urgent care clinic. She develops widespread urticaria, hoarse voice, and progressive breathlessness.

Initial observations show tachycardia and hypotension. She receives intramuscular adrenaline 0.5 mg, high-flow oxygen, and a rapid IV crystalloid bolus. Five minutes later, her blood pressure remains low and wheeze persists. A second IM adrenaline dose is administered appropriately.

After a further 5 minutes, she continues to have persistent stridor and hypotension despite ongoing oxygen and fluids.

Which of the following best defines this clinical situation?