Allergy - 2. Anaphylaxis: diagnosis and management

Anaphylaxis is a serious, rapid-onset, allergic reaction that may cause death. Severe anaphylaxis is c'haracterised by life-threatening upper airway obstruction, bronchospasm and/or hypotension. Anaphylaxis in children is most often caused by food. Bronchospasm is a common symptom, and there is usually a background of atopy and asthma. Venom- and drug-induced anaphylaxis are more common in adults, in whom hypotension is more likely to occur. Diagnosis can be difficult, with skin features being absent in up to 20% of people. Anaphylaxis must be considered as a differential diagnosis for any acute-onset respiratory distress, bronchospasm, hypotension or cardiac arrest. The cornerstones of initial management are putting the patient in the supine position, administering intramuscular adrenaline into the lateral thigh, resuscitation with intravenous fluid, support of the airway and ventilation, and giving supplementary oxygen. If the response to initial management is inadequate, intravenous infusion of adrenaline should be commenced. Use of vasopressors should be considered if hypotension persists. The patient should be observed for at least 4 hours after symptom resolution and referred to an allergist to assist with diagnosis, allergen avoidance measures, risk assessment, preparation of an action plan and education on the use of self-injectable adrenaline. Provision of a MedicAlert bracelet should also be arranged.