What is the initial treatment for a patient presenting with acute urticaria according to American Academy of Family Physicians (AAFP) guidelines?

Initial Treatment for Acute Urticaria

Begin immediately with a second-generation non-sedating H1 antihistamine such as cetirizine, loratadine, fexofenadine, levocetirizine, or desloratadine at standard dosing. 1, 2

First-Line Antihistamine Therapy

• Second-generation antihistamines are the definitive cornerstone of acute urticaria management, with cetirizine, desloratadine, fexofenadine, levocetirizine, and loratadine as preferred options 1, 2
• Offer at least two different antihistamine options to trial, as individual responses and tolerance vary significantly between agents 1, 2
• Cetirizine reaches maximum concentration fastest, making it advantageous when rapid symptom relief is needed 1
• Avoid first-generation antihistamines (diphenhydramine, hydroxyzine, chlorpheniramine) as primary therapy due to significant sedation and potential to worsen outcomes in severe reactions 2

Dose Escalation for Inadequate Response

• If standard dosing provides inadequate control within 24-48 hours, increase the antihistamine dose up to 4 times the standard dose 1, 2
• This escalation strategy should be implemented before adding other therapies 1

Role of Corticosteroids in Moderate to Severe Cases

Add a short course of oral corticosteroids (prednisolone 50 mg daily for 3 days) for moderate to severe acute urticaria, rather than waiting for antihistamine failure. 2, 3

• Short courses of 3-10 days can achieve complete remission in a significant proportion of patients 2
• In one high-quality RCT, 93.8% of corticosteroid-treated patients achieved complete remission within 3 days compared to 65.9% with antihistamine alone 3
• Restrict corticosteroids to short courses only due to cumulative dose- and time-dependent toxicity 2
• Never use corticosteroids for chronic management 1, 2

Critical Distinction: Anaphylaxis vs. Urticaria

If acute urticaria presents with signs of anaphylaxis (hypotension, angioedema of tongue/airway, respiratory compromise, or involvement of 2+ organ systems), immediately administer intramuscular epinephrine 0.5 mL of 1:1000 solution (500 µg) into the anterolateral thigh. 2, 4

• Antihistamines and corticosteroids are adjunctive only in anaphylaxis—never use them in place of epinephrine 1
• Antihistamines take 30-120 minutes to reach peak plasma concentrations and lack the vasoconstrictive, bronchodilatory, and mast cell stabilization properties of epinephrine 1

Adjunctive Measures

• Identify and eliminate triggering factors immediately, including upper respiratory tract infections (most common at 39.5%), analgesics, and NSAIDs 2, 3
• Avoid aspirin, NSAIDs, and codeine in all patients until triggers are clarified 1, 2
• Apply cooling antipruritic lotions (calamine or 1% menthol in aqueous cream) for symptomatic relief while waiting for pharmacotherapy to take effect 2

Common Pitfalls to Avoid

• Never use first-generation antihistamines in acute infusion reactions, as they can exacerbate hypotension, tachycardia, and shock 1
• Do not continue corticosteroids beyond short courses, as the evidence for prolonged benefit is questionable and toxicity accumulates 2
• Corticosteroids have slow onset of action and work by inhibiting gene expression—they are ineffective for acute symptom relief 1

Expected Clinical Course

• Acute urticaria is largely self-limited, with the longest episodes lasting up to 3 weeks 3
• Approximately 50% of patients with acute urticaria presenting with wheals alone will be clear by 6 months 1, 2
• Most cases are idiopathic (identified triggers in less than 50% of cases) and only rarely associated with IgE-mediated events 3