Treatment of Sudden Bouts of Hives (Acute Urticaria)
Administer cetirizine 10 mg IV or PO immediately as the preferred first-line agent for acute urticaria, with observation for 90 minutes to monitor response and rule out progression to anaphylaxis. 1
Immediate Management
- Cetirizine 10 mg IV or PO is the preferred initial agent due to its rapid onset and effectiveness in acute urticaria 1
- Alternative second-generation antihistamines include loratadine 10 mg PO if cetirizine is unavailable or not tolerated 1, 2
- Second-generation H1 antihistamines are the mainstay of therapy for both acute and chronic urticaria 3, 4
Critical Assessment During Initial Observation
- Observe for 90 minutes after initial dose to assess response and monitor for symptom progression 1
- Rule out anaphylaxis by actively assessing for:
- Isolated urticaria without systemic symptoms should be distinguished from anaphylaxis, as the former may respond to antihistamines alone while the latter requires immediate epinephrine 5
Important Caveat: When Hives Signal Danger
- If hives appear after exposure to a known allergen that previously caused anaphylaxis, administer epinephrine immediately rather than waiting for additional symptoms to develop 6
- Generalized acute urticaria can be the first symptom of developing anaphylaxis, particularly in high-risk situations 6
- Severe life-threatening symptoms can appear suddenly even after hives have disappeared with antihistamine treatment 6
- Biphasic reactions can occur 6-12 hours after initial symptoms resolve, necessitating extended observation in high-risk cases 6
Escalation Strategy for Inadequate Response
If symptoms persist or worsen despite initial antihistamine therapy:
- Add a short course of oral corticosteroids (prednisone 0.5-1 mg/kg/day PO for 3-10 days) for severe acute exacerbations 1
- Consider switching to a different second-generation antihistamine such as desloratadine 5 mg daily or levocetirizine 5 mg daily if cetirizine is ineffective 1
- Corticosteroids may be used acutely but should not be used long-term 7
Identify and Remove Triggers
- Assess for potential medication triggers including NSAIDs, aspirin, ACE inhibitors, and codeine, as these can precipitate or worsen urticaria 1
- ACE inhibitors should be avoided if any component of angioedema is present, as 3-5% of patients on ACE inhibitors develop angioedema 1, 7
- In acute episodic urticaria (most common in children and young adults), common triggers include viral infections, allergic reactions to foods and drugs, contact with chemicals, and physical stimuli 8
Adjunctive Symptomatic Measures
- Apply cooling antipruritic lotions such as calamine or 1% menthol in aqueous cream for additional symptomatic relief 1
- Minimize aggravating factors including overheating, stress, and alcohol 1
Common Pitfalls to Avoid
- Do not assume absence of respiratory or cardiovascular symptoms guarantees they won't develop - acute urticaria can rapidly progress to anaphylaxis 6
- Do not rely on first-generation antihistamines (like diphenhydramine) as first-line therapy when second-generation agents are available, as they cause sedation and have shorter duration of action 1, 3
- Do not delay epinephrine in patients with known severe allergies who develop hives after allergen exposure, even if other symptoms are absent 6
- Do not use long-term corticosteroids for urticaria management - they are appropriate only for short courses in severe acute exacerbations 1, 7
When to Consider Chronic Urticaria
If urticaria persists beyond 6 weeks, transition to chronic urticaria management:
- Continue high-dose second-generation antihistamines (up to 4x standard dose) as first-line therapy 1, 9
- Add omalizumab 300 mg subcutaneously every 4 weeks if inadequate response to high-dose antihistamines after 2-4 weeks 1, 9
- Approximately 40% of patients respond to standard-dose antihistamines, while others require dose escalation or additional therapies 9