• Angio-oedema is a swelling in the dermis, subcutaneous and submucosal tissues which can occur with or without urticaria. For more information see the CKS topic on Urticaria.
• Swellings can occur anywhere on the body, but most often involve the eyes, lips, genitalia, and hands or feet.
• Systemic involvement can occur affecting the bowel and the airway (when you should consider early anaphylaxis).
• Angio-oedema may be considered part of the continuum of anaphylaxis but, in isolation, without respiratory difficulty is not anaphylaxis.
• Anaphylaxis means a severe life-threatening systemic hypersensitivity reaction. There is no accepted universal definition for anaphylaxis and the problem is which clinical features are essential for the diagnosis:
• Rapidly developing airway and/or breathing difficulty and/or hypotension should be present when defining anaphylaxis [Ewan, 1998; Working Group of the Resuscitation Council (UK), 2008].
• Other features of an allergic reaction are often present, but without respiratory difficulty or hypotension the reaction is not strictly anaphylaxis:
• Skin and mucosal features include angio-oedema of the face and urticaria.
• Systemic features include abdominal pain, vomiting, and rhinitis.
• The mechanism for angio-oedema and anaphylaxis is the same, both histamine and bradykinin are involved. In anaphylaxis the reaction is more marked, resulting in an increase in vascular permeability and subsequent circulatory collapse.

[Kobza-Black and Champion, 1998; Joint Task Force on Practice Parameters for Allergy & Immunology, 2005; Working Group of the Resuscitation Council (UK), 2008]