Differential Diagnosis of Anaphylaxis
| Diagnosis | Comment |
|---|---|
| Chronic spontaneous urticaria and angioedema | Background of symptoms daily for >6 weeks Rapid development of symptoms rare Stridor may develop due to laryngeal oedema Hypotension and wheeze not typical |
| ACE-inhibitor-induced angioedema | Swelling affects head and neck only Stridor may develop due to laryngeal oedema; if life-threatening airways obstruction treat with icatibant No urticaria or hypotension May develop days to years after starting ACE-inhibitor; may persist for some weeks after ACEI discontinuation |
| Hereditary angioedema | Urticaria and hypotension absent Stridor (due to laryngeal oedema) rather than wheeze Usually personal or family history Treat with C1-esterase inhibitor (either plasma-derived or recombinant human C1 inhibitor or icatibant; fresh frozen plasma may be used if neither of these available) |
| Acute asthma | No itch, urticaria or angioedema Hypotension late feature |
| Acute heart failure | No itch, urticaria or angioedema |
| Scombrotoxin poisoning | Caused by bacterial overgrowth in improperly stored dark-meat fish (e.g. tuna, mackerel) Symptoms appear within 30 min of eating spoiled fish: urticarial, nausea, vomiting, diarrhoea, headache, metallic taste Treat with antihistamine |
| Vasovagal reaction | No itch, urticaria or angioedema |
| Acute panic disorder | No itch, urticaria, angioedema, hypoxia or hypotension Functional stridor may develop as a result of forced adduction of vocal cords |
ACE, angiotensin-converting enzyme.