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)
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.