Hypertensive Anaphylaxis in the Emergency Department: A Case Series

Anaphylaxis is a rapid-onset, life-threatening allergic reaction that classically presents with hypotension and distributive shock. Hypertension is generally considered atypical in this context and may delay recognition of anaphylaxis in the emergency department. However, case reports and small studies have described paradoxical "hypertensive anaphylaxis," with reported prevalence rates of up to 12.9%. Awareness of this variant is essential to avoid withholding timely epinephrine therapy. We describe four adults who presented to the emergency department with systemic allergic reactions characterized by urticaria, angioedema, dyspnea, and gastrointestinal involvement. All four patients were initially normotensive but subsequently developed paradoxical hypertension, with blood pressures ranging from 140/90 mmHg to 168/102 mmHg at the time of anaphylaxis. Triggers included intravenous fluids, medications, and an insect bite. Each patient received intramuscular epinephrine (0.5 mg), intravenous fluids, corticosteroids, antihistamines, and inhaled bronchodilators where appropriate. Two patients required repeat epinephrine dosing for persistent symptoms. Despite presenting with elevated blood pressure, all patients tolerated epinephrine without any complications related to the catecholamine surge, such as arrhythmia, myocardial ischemia, or intracranial events. All recovered fully and were discharged after a short period of hospital observation. This case series reinforces that hypertension does not preclude the diagnosis of anaphylaxis and should not deter clinicians from administering first-line epinephrine. The pathophysiology of hypertensive anaphylaxis is not fully understood but may involve compensatory sympathetic activation, endogenous catecholamine release, or anxiety-mediated responses. Recognition of this variant is critical for emergency physicians, as reliance on hypotension as a diagnostic criterion can delay life-saving treatment. In conclusion, hypertensive anaphylaxis represents an under-recognized clinical presentation. Our four cases add to the growing body of literature confirming that intramuscular epinephrine is safe and effective, even in the setting of elevated blood pressure. Emergency clinicians should base the diagnosis of anaphylaxis on systemic features rather than hemodynamic profile, ensuring that adrenaline administration is not delayed by paradoxical hypertension.