What is the best course of treatment for a pediatric patient presenting with idiopathic urticaria (hives) and no known triggers?

Treatment of Idiopathic Urticaria in Pediatric Patients

For a pediatric patient with idiopathic urticaria (hives with no known triggers), start with a non-sedating H1 antihistamine as first-line therapy, such as cetirizine or loratadine, dosed by weight, and escalate the dose up to 4 times the standard dose if symptoms persist after 24-48 hours. 1, 2

Initial Assessment and Risk Stratification

Before initiating treatment, determine whether this is isolated urticaria or part of a systemic reaction:

• Isolated hives without respiratory symptoms, tongue/lip swelling, or cardiovascular symptoms can be managed with antihistamines alone 1, 2
• Hives with any respiratory symptoms (wheezing, stridor, difficulty breathing), significant tongue/lip swelling, or signs of cardiovascular compromise require immediate intramuscular epinephrine 0.01 mg/kg (maximum 0.3 mg) in the anterolateral thigh, NOT antihistamines 1, 3, 4
• Generalized urticaria after insect sting warrants epinephrine prescription due to ~10% risk of severe future reactions 1

A critical pitfall is delaying epinephrine administration in favor of antihistamines when anaphylaxis is developing—hives can be the first symptom of anaphylaxis, which can progress rapidly 2, 4

First-Line Pharmacotherapy

Non-sedating H1 antihistamines are the cornerstone of treatment for isolated urticaria:

• Cetirizine: Weight-based dosing (typically 0.25 mg/kg/dose once daily for children 6 months-5 years; 5-10 mg daily for older children), fastest time to maximum concentration but may be mildly sedating at higher doses 1, 2
• Loratadine: 5 mg daily for children 2-5 years, 10 mg daily for children ≥6 years 2, 5
• Desloratadine: Has the longest elimination half-life at 27 hours, providing sustained coverage 2

The British Journal of Dermatology recommends offering at least two different non-sedating antihistamines as options, since individual responses vary significantly 2

Dose Escalation Strategy

If symptoms persist after 24-48 hours on standard dosing:

• Increase the antihistamine dose up to 4 times the standard dose when benefits outweigh risks 1, 2
• Adjust timing of medication to ensure highest drug levels coincide with anticipated urticaria episodes 2
• This dose escalation is supported by guidelines and is more effective than adding multiple different medications at standard doses 1, 2

Adjunctive Therapies

If high-dose H1 antihistamines are insufficient:

• Add an H2 antihistamine (such as ranitidine 2-4 mg/kg/day divided twice daily in children) for enhanced symptom control—the combination of H1 and H2 blockers provides superior relief compared to H1 blockers alone 2, 6
• Consider antileukotriene agents (montelukast) as they may benefit a subset of patients, though evidence is limited 1, 6
• Short course of oral corticosteroids (prednisone 1 mg/kg, maximum 60-80 mg daily for 3-5 days) for severe acute urticaria, though this should not be used long-term 1, 3, 6

First-generation antihistamines like diphenhydramine can be used but are not preferred due to sedation and shorter duration of action 3, 7

When to Prescribe Epinephrine Auto-Injector

Prescribe an epinephrine auto-injector (two doses) with appropriate training if: 1, 2

• The urticaria episode was moderate-to-severe, indicating higher risk for future severe reactions
• There is history of generalized urticaria after insect sting
• The patient has coexisting asthma (higher risk for severe reactions) 1, 4
• The patient lives in a remote area away from medical care 1

Dosing: 0.15 mg for patients <25 kg, 0.3 mg for patients ≥25 kg 2

Diagnostic Workup for Idiopathic Urticaria

For acute urticaria (<6 weeks), extensive laboratory testing is not indicated unless the history or physical examination suggests specific underlying conditions 1, 8

For chronic urticaria (≥6 weeks), consider limited testing: 1, 9

• Complete blood count with differential
• C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR)
• Total IgE level
• IgG-anti-thyroid peroxidase (anti-TPO) antibodies

Important distinction: If angioedema occurs WITHOUT urticaria (wheals), immediately order C4 level, C1 inhibitor antigen, and C1 inhibitor functional activity to screen for hereditary or acquired C1 inhibitor deficiency—these patients will not respond to antihistamines 1, 9

Referral to Allergist-Immunologist

Refer to an allergist-immunologist for: 1, 3, 2

• Chronic urticaria (lesions recurring persistently over ≥6 weeks)
• Identification of triggers through detailed history, possible skin testing, and physical challenges
• Optimal pharmacotherapy management
• Education on avoidance of identified allergens
• Development of an emergency action plan

Allergist-immunologists have more expertise in caring for patients with urticaria than other specialists and can provide appropriate differential diagnosis and advanced treatments if first-line therapies fail 1

Patient and Family Education

Provide clear instructions on: 3, 2

• When to use antihistamines: For mild symptoms (a few hives, mild itch)
• When to use epinephrine (if prescribed): For diffuse hives, any respiratory symptoms, obstructive swelling of tongue/lips interfering with breathing, or circulatory symptoms
• Warning signs requiring emergency care: Breathing difficulty, widespread worsening urticaria, facial/throat swelling
• Expected course: Urticaria may recur over the next 1-2 days even after stopping the trigger—this is expected and does not indicate treatment failure

Cooling antipruritic lotions (calamine or 1% menthol in aqueous cream) can provide symptomatic relief 2

Follow-Up and Monitoring

• Schedule follow-up in 3-5 days to ensure complete resolution 2
• For chronic urticaria, use validated tools like the 7-Day Urticaria Activity Score or Urticaria Control Test to assess disease control 9
• More than one-half of patients with chronic urticaria will have resolution or improvement of symptoms within a year 8