Diagnosis of Anaphylaxis

Diagnosing Anaphylaxis

Anaphylaxis can be difficult to diagnose. Consideration should be given to the following questions to aid diagnosis:

  • Is there a sudden onset and rapid progression of symptoms?
  • Are there life threatening changes to the respiratory and/or circulatory system?
  • Are there skin and/or mucosal changes?
  • Has the patient been exposed to a known allergen?
  • Remember:skin or mucosal changes alone are not a sign of an anaphylactic reaction
  • skin and mucosal changes can be subtle or absent in up to 20% of reactions (some patients can have only a decrease in blood pressure, i.e. a circulation problem)
  • there can also be gastrointestinal symptoms (e.g. vomiting, nausea, abdominal pain, severe colic, incontinence, uterine cramps in menstruating girls/women)

Differential Diagnosis

There are other conditions which can look like anaphylaxis, and this could add to the diagnostic difficulty when assessing a patient.

  • Some examples would include:severe asthma – if in doubt, treat as anaphylaxis
  • septic shock – low blood pressure and petechial or purpuric rash
  • fainting (vasovagal episode)
  • breath holding in children 
  • idiopathic urticarial or angioedema.

Patients who have had previous anaphylactic reactions may be prone to panic attacks if they think they have been re-exposed to an allergen.