Urticaria

Fact sheet

Rash due to mast cell degranulation resulting in histamine release due to immune or non-immune triggers

  • Most are acute (<6 weeks), resolve spontaneously, and do not require extensive investigation

  • Chronic spontaneous urticaria is recurrent and lasts >6 weeks, possibly months to years, and is usually autoimmune or idiopathic

  • Episodic

Assessment

  • Rash history

    • Shapes, size, duration, distribution

    • Associated features like angioedema

    • Aggravating factors (hot, cold, tight clothing, NSAIDs, alcohol, stress

    • Response to medications

    • Frequency, timing, duration, pattern of recurrence

  • Exam

    • Transient itchy pink or white wheals

    • Well-circumscribed, mm to cm, coalescing

  • DDX

    • Urticarial vasculitiss if persistent

    • Systemic symptoms may indicate an underlying systemic autoimmune disease

    • Episodic linear urticaria may be larva currens

Triggers

  • Helicobacter pylori

  • Salicylates (tomato, capsicum, red wine, berries, nuts, shellfish)

  • Heat or exercise

  • Cold

  • Pressure

  • Sun exposure

  • Medications (Aspirin, NSAIDs, opioids, ACEI, ABx)

Management

  • Treat anaphylaxis as appropriate

  • Avoid identifiable triggers

  • Treat any obvious underlying causes

  • Medication

    • Antihistamine H1, up titrate to 4 x the standard daily dose is safe

    • If significant nocturnal itch, consider substituting doxepin for the night dose e.g. 10mg nocte

    • Antihistamine doses

    • Can trial H2 antihistamines (Ranitidine)

    • If needed, especially if prominent angioedema, consider Pred 20-25mg tapering over 10 days.

References