Clinical investigations from the RACP

The investigation of anaphylaxis

Richard Steele



The investigation of a patient who presents after an episode of anaphylaxis can be challenging and rewarding. It requires an understanding of the underlying mechanisms resulting in anaphylaxis, knowledge of the common causes and well-directed questioning of the patient.

Key Points

  • Always consider the differential diagnoses for anaphylaxis, including vasovagal episodes, pulmonary embolus and other causes of hypotension.
  • The common causes of anaphylaxis are insect venoms, foods and medications.
  • In up to one-third of cases, the trigger for the anaphylaxis is not found; this is called idiopathic anaphylaxis.
  • Food is a more common trigger for anaphylaxis in children, medications are more common triggers in adults.
  • The use of skin and radioallergosorbent testing should be based on the history; these tests can be useful to confirm IgE-mediated reactions.