How should I manage a 59 kg patient who presents with acute urticaria (wheals) on the back?

Management of Acute Urticaria (Wheals) on the Back in a 59 kg Patient

Start with a high-dose second-generation H1 antihistamine immediately; this is the cornerstone of treatment for acute urticaria and should be continued for at least 3 days. 1, 2

Immediate Assessment

Before initiating treatment, quickly determine whether this is simple acute urticaria or a more serious condition:

• Confirm the lesions are true wheals: Individual lesions should resolve within 2–24 hours without leaving scars or bruising. 1 If wheals persist beyond 24 hours, suspect urticarial vasculitis and consider biopsy. 1

• Rule out anaphylaxis: Check for hypotension, hypoxia, respiratory distress, or laryngeal edema. If any are present, give intramuscular epinephrine immediately (0.3–0.5 mg for adults) and provide supportive care. 1, 3, 4 For a 59 kg patient, use the standard adult dose.

• Assess for angioedema: If there is non-itchy deep tissue swelling without wheals, consider C1-esterase inhibitor deficiency or ACE-inhibitor-induced angioedema—antihistamines and corticosteroids will be ineffective in these cases. 1, 3

First-Line Pharmacologic Treatment

Second-generation H1 antihistamines are the treatment of choice and can be titrated up to four times the standard dose if needed. 1, 2, 5

• Start with standard dosing (e.g., cetirizine 10 mg, loratadine 10 mg, or fexofenadine 180 mg daily). 2, 5
• If symptoms persist after 24–48 hours, increase to double or quadruple the standard dose. 2, 5
• Continue treatment for at least 3 days, even if symptoms improve earlier. 6
• Avoid first-generation sedating antihistamines in elderly patients due to anticholinergic side effects. 7

Adjunctive Therapy

A short course of oral corticosteroids (prednisolone 50 mg daily for 3 days) can shorten the duration of acute urticaria, particularly in moderate to severe cases. 1, 6

• Corticosteroids are more effective than antihistamines alone for rapid symptom resolution: 93.8% of patients achieve complete remission within 3 days with corticosteroids versus 65.9% with antihistamines alone. 6
• Use the lowest effective dose for the shortest duration (typically 3 days). 1, 6
• Do not use long-term corticosteroids—they cause significant morbidity and are not indicated for routine acute urticaria. 1, 3

Supportive Measures and Trigger Avoidance

• Avoid aspirin and NSAIDs: These can trigger mast cell degranulation and worsen urticaria. 1, 3
• Avoid alcohol: It can exacerbate symptoms. 1, 3
• Apply topical cooling agents (calamine lotion or 1% menthol in aqueous cream) for symptomatic itch relief. 1
• Counsel the patient to avoid overheating, emotional stress, and tight clothing. 1

Diagnostic Workup

No routine laboratory testing is required for typical acute urticaria. 1, 3

• The diagnosis is clinical. 1, 2, 5
• Investigations are only indicated if the history suggests a specific trigger (e.g., food allergy, drug reaction) or if the presentation is atypical. 1
• If an IgE-mediated allergy is suspected, perform skin-prick testing or specific IgE assays. 1
• If wheals persist beyond 24 hours or leave bruising, obtain a lesional skin biopsy to rule out urticarial vasculitis. 1

Common Pitfalls

• Do not prescribe an epinephrine autoinjector for simple acute urticaria without evidence of anaphylaxis. 3 Epinephrine is only indicated if the patient has had hypotension, hypoxia, or respiratory compromise requiring acute epinephrine treatment. 3
• Do not perform extensive laboratory workups (CBC, ESR, thyroid antibodies) for acute urticaria—these are only useful in chronic urticaria (>6 weeks duration). 1, 3
• Do not assume this is an "allergic reaction": Most acute urticaria is post-infectious or idiopathic, not IgE-mediated. 3, 6 Possible triggers are identified in less than 50% of cases. 6
• Do not add H2 antihistamines routinely: The evidence for benefit is limited and mainly applies to associated dyspepsia. 1

Prognosis and Follow-Up

• Acute urticaria is self-limited in all cases, with most episodes resolving within 3 days to 3 weeks. 6
• If symptoms persist beyond 6 weeks, the condition is reclassified as chronic urticaria and warrants further evaluation. 2, 5
• More than half of patients with chronic urticaria will have resolution or improvement within one year. 2, 5