Treatment of Allergic Reaction with Hives and No Airway Compromise
For isolated urticaria without airway compromise, start immediately with a non-sedating second-generation H1 antihistamine such as cetirizine 10 mg, loratadine 10 mg, fexofenadine 180 mg, or levocetirizine 5 mg daily, and consider adding an H2 antihistamine (ranitidine) and a short course of oral corticosteroids (prednisone) for more rapid and complete symptom control. 1, 2
Acute Management Algorithm
First-Line Treatment: H1 Antihistamines
Administer a non-sedating second-generation H1 antihistamine immediately as the primary treatment for isolated urticaria 1, 2
- Options include: cetirizine 10 mg daily, loratadine 10 mg daily, fexofenadine 180 mg daily, or levocetirizine 5 mg daily 1, 2
- Second-generation agents are preferred over diphenhydramine due to comparable onset of action (no statistically significant difference in time to 50% symptom reduction) but superior safety profile with less sedation 3
If inadequate response within 24-48 hours, increase the antihistamine dose up to 4 times the standard dose (e.g., cetirizine 40 mg daily) 1, 2
Adjunctive Therapy for Enhanced Control
Add an H2 antihistamine (ranitidine 1-2 mg/kg per dose, maximum 75-150 mg) twice daily for 2-3 days 4
- The combination of H1 and H2 antihistamines provides superior relief for urticaria compared to H1 antihistamines alone, with 92% of patients achieving clinically significant relief versus 46% with H1 alone 5
Consider oral corticosteroids for more severe or generalized hives: prednisone 0.5-1 mg/kg daily (typically 40-60 mg for adults, maximum 60-80 mg) for 2-3 days 4, 1
- Short courses are recommended to accelerate resolution and prevent progression 2
Critical Patient Education Points
Warn the patient that recurrent urticaria may occur over the next 1-2 days even after stopping the triggering agent, which is expected and does not indicate treatment failure 1, 2
Document the allergen prominently in the medical record if a specific trigger (medication, food) is identified 1
Provide an emergency action plan instructing the patient to seek immediate care if breathing difficulty, widespread urticaria, or facial/throat swelling develops 1, 2
When to Consider Epinephrine
Epinephrine is NOT indicated for isolated urticaria without systemic symptoms 4, 6. However, the guidelines specify epinephrine as first-line treatment only when anaphylaxis is present, defined by signs including respiratory symptoms, hypotension, gastrointestinal symptoms, or airway compromise 4, 6.
- Consider prescribing an epinephrine auto-injector for discharge if the patient had moderate-to-severe urticaria, as this indicates higher risk for future severe reactions 1
- Dosing: 0.15 mg for 10-25 kg; 0.3 mg for >25 kg 4
Discharge Planning
Continue H1 antihistamine (diphenhydramine or non-sedating alternative) every 6 hours for 2-3 days 4
Continue H2 antihistamine (ranitidine) twice daily for 2-3 days 4
Continue corticosteroid (prednisone) daily for 2-3 days if initiated 4
Schedule follow-up in 3-5 days to ensure complete resolution and adequate symptom control 1
Consider referral to an allergist for identification of triggering allergen and long-term management 4
Common Pitfalls to Avoid
Do not rely solely on diphenhydramine when second-generation antihistamines are available, as they have equivalent efficacy with better tolerability 3, 7
Do not administer epinephrine for isolated urticaria without signs of anaphylaxis, as this represents overtreatment and unnecessary risk 4, 6
Do not assume symptom resolution means the reaction is complete—patients must be counseled about potential recurrence over 1-2 days 1, 2