INDEX

    Acute Urticaria

    Dermatology, Pediatrics

    Last Updated Oct 25, 2020
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    Context

    • Urticaria (“Hives”) is a common disorder presenting with a pruritic, well circumscribed, raised, erythematous plaques (Figure 1).
      • Lesions are typically transient and migratory, lasting minutes to hours.
      • Typically painless.
      • Variable size, and may coalesce together to form large plaques.

    Figure 1. Classic appearance of urticaria.

    • Urticaria may be acute or chronic – this article will primarily address acute urticaria.
      • Acute urticaria – present for < 6 weeks.
      • Chronic urticaria – recurring symptoms, present most days for 6 weeks or longer.
    • May be associated with angioedema, as in the case of histamine-mediated reactions including anaphylaxis.
    • Common causes of urticaria:
      • Allergic reactions (food, medications, arthropods).
      • Infection (viral, bacterial, parasitic).
      • Direct Non-allergic Mast Cell activation (radiocontrast, foods, stinging nettle, medications e.g. NSAIDs, narcotics).
      • Systemic Disease (autoimmune disorders, vasculitis, malignancy).
      • Scombroid Syndrome (ingestion of improperly stored fish):
        • Tuna mackerel, mahi mahi, sardine, anchovy, herring etc. naturally have high levels of histidine, which is converted to histamine by bacteria.
        • flushed skin, headache, itchiness, blurred vision, abdominal cramps, and diarrhea.
    •  Patients will typically present to the emergency department with an itchy red rash.

    Diagnostic Process

    • The initial priority for any patient with acute urticaria is to exclude anaphylaxis which requires urgent diagnosis and treatment.
    • The diagnosis of urticaria is based on clinical features alone. The term “hives” is used non-specifically by patients, but the diagnosis is generally fairly simple for clinicians. Often the lesions may have resolved at the time of evaluation, and photographs from earlier episodes can be very useful.
    • Determine whether this is acute or chronic urticaria.
    • Diagnosis of the cause of acute urticaria requires a more detailed history, physical exam and consideration of selected laboratory or provocative testing.
      • Attempt to identify an obvious trigger (infection, allergy, etc.)
      • Screening should be performed to assess for an underlying systemic disorder.
        • Laboratory testing or imaging may be indicated for patient who screen positive.
          • Vasculitis: Lesions often painful, last for >24h in a single location, transition to purpura/bruising and B-symptoms.
          • Malignancy: Urticaria will become chronic (>6 weeks), B-symptoms.
          • Auto-immune: Routine screening only necessary if other features of auto-immune disease or prior history.
      •  Consider allergy testing or referral to an allergy and immunology specialist.

    Recommended Treatment

    • The majority of acute urticaria will be self-limited and resolve spontaneously, and the priority once anaphylaxis has been excluded is to control patient symptoms.
    • Consider admission for observation of any patients with significant associated angioedema that does not resolve with treatment.
    • Symptomatic management:
      • General Approach:
        • H1 non-sedating Antihistamines for all patients:
          • Continue for at least 1 week for severe symptoms or if receiving glucocorticoids.
        • H2 Antihistamines for more severe symptoms.
        • Short course glucocorticoids (5-7 days) for patients with associated angioedema or refractory symptoms.
      • H1 Antihistamines:
        • First generation:
          • Diphenhydramine 50mg PO/IV/IM q6-8h.
          • Hydroxyzine 50mg PO/IM q6-8h.
        • Second generation non-sedating (preferred – any agent):
          • Loratadine 10-20mg PO daily.
          • Cetirizine 10-20mg PO daily.
          • Fexofenadine 180mg PO daily.
        • H2 Antihistamines:
          • Ranitidine 50mg IV q6-8h or 150mg PO BID.
          • Famotidine 10-20mg PO BID.
        • Glucocorticoids:
          • Prednisone 50-60mg PO daily x 5-7 days.
    • Patients with any suspicion for allergic reaction should be prescribed an epinephrine auto-injector on discharge and referred to an allergist.
    • Patients with undifferentiated recurrent or difficult to control urticaria without obvious treatable trigger can be referred to an allergist for further evaluation and testing.

    Quality Of Evidence?

    Justification

    Evidence primarily comprised of low to moderate quality randomized trials with limitations, or from international guidelines.

    Moderate

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