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  • diagnosis is mainly clinical
    • a careful history and examination will be sufficient to make the diagnosis in most of the patients
      • detailed history - change in diet, medication; illness
      • examination - characteristic raised areas of the skin (weals) with redness in the surrounding area, blotchy areas can be seen when the weals fade before the surrounding area (1)
        • dermographism may be evident
  • the list of possible investigations is vast considering most cases are idiopathic
      • FBC - Hb, WBC, eosinophils, platelets
      • ESR
      • LFT's
      • Thyroid function test and thyroid autoantibodies
      • chest and sinus X-ray
      • urinalysis - bacteria
      • stool analysis - parasites
      • complement screen - including C1 esterase inhibitor
      • antinuclear antibody " skin biopsy - for urticarial vasculitis (2)
    • a good initial screening investigation is an ESR
  • the duration of weal's can be used to differentiate the clinical patterns of urticaria:
    • ordinary urticaria - weals usually lasts from 2 to 24 hours
    • contact urticaria - upto 2 hours
    • physical urticaria - disappear within an hour, in delayed pressure urticaria takes upto 2-6 hours to develop and upto 48 hours to fade
    • urticarial vasculitis - persist for days
    • angioedema - can last upto 3 days without treatment (2)



Last reviewed 01/2018