Angioedema and Anaphylaxis

🔍 When to Suspect

Rapid onset of deep, non-pitting swelling (angioedema), especially with systemic features (difficulty breathing, wheeze, dizziness), suggesting anaphylaxis

From the full topic in The Ocean Library: Angioedema and Anaphylaxis

🧭 When to suspect

Anaphylaxis is a severe, life-threatening, generalised hypersensitivity reaction. It is a clinical diagnosis resting on three features: sudden onset, rapid progression, and a life-threatening Airway, Breathing or Circulation (ABC) problem. Skin and mucosal changes (urticaria, flushing, angio-oedema) accompany most cases but are absent in up to 20% – so their absence never excludes the diagnosis. Exposure to a known allergen supports it, yet no trigger is found in around 30% (idiopathic).

Angio-oedema is self-limiting deep dermal and subcutaneous swelling (lips, tongue, eyelids, genitalia, hands, feet), typically non-itchy and tight rather than the itchy weals of urticaria, and may take up to 72 hours to settle. The decisive question is mechanism: histaminergic (mast-cell / allergic, responds to antihistamines and adrenaline) versus bradykinin-mediated (ACE inhibitor or hereditary), which does not respond to antihistamines, steroids or adrenaline. The two primary-care priorities are to never miss evolving anaphylaxis – any ABC involvement means IM adrenaline now – and to identify and remove the trigger.

Pattern	Recognise it by	First action
Anaphylaxis	Sudden onset, rapid progression, life-threatening Airway and/or Breathing and/or Circulation problem; skin changes usual but absent in up to 20%	IM adrenaline now + call 999
Histaminergic angio-oedema (± urticaria)	Itchy swelling, often with weals; mast-cell / allergic; lips, eyelids, tongue	Non-sedating antihistamine; treat as anaphylaxis if any ABC involvement
Bradykinin-mediated angio-oedema (ACE inhibitor or hereditary)	Non-itchy, no weals, slower onset, face / tongue / larynx; poor response to antihistamine, steroid and adrenaline	Stop the ACE inhibitor; protect the airway; specialist (C1-INH / icatibant) if airway threatened

Source: Resuscitation Council UK · NICE NG258

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