What are the typical presentation and treatment of urticaria in children?

Presentation of Urticaria in Children

Urticaria in children typically presents as transient, itchy wheals (hives) that last 2-24 hours, often appearing as large, annular or geographic plaques in infants, with acute forms being most common and frequently triggered by viral infections. 1, 2

Clinical Presentation

Morphology and Distribution

• Wheals are characterized by erythematous, raised, itchy lesions that can vary from millimeters to centimeters in size and appear anywhere on the body 3
• In newborns and infants specifically, urticaria typically presents as generalized, large, annular, or geographic plaques that are often slightly raised, reflecting the unique structure of neonatal and infant skin 2
• Individual wheals in ordinary urticaria last 2-24 hours before resolving without scarring 1

Associated Features

• Approximately 40% of pediatric patients develop accompanying angioedema, which involves localized deep tissue swelling affecting lips, eyelids, palms, soles, and genitalia 3, 4
• Angioedema may persist up to 3 days without treatment 1
• The pruritus (itching) can be severe and significantly impact quality of life 4

Classification by Duration

Acute Urticaria (Most Common in Children)

• Acute urticaria lasts less than 6 weeks and is the predominant form in the pediatric population 5, 3
• Often presents as a recurrent phenomenon (recurrent urticaria) 5
• Typically self-limiting in nature 3

Chronic Urticaria

• Defined as hives and/or angioedema persisting for more than 6 weeks 6
• Prevalence in general population ranges from 0.5-5% 3
• Can be either spontaneous or inducible 3

Common Triggers and Etiology

Acute Urticaria Triggers

• Viral infections are the most common cause of acute urticaria in children 5, 6
• Other triggers include:
  • Allergic reactions to foods (most commonly egg in infants) 5, 4
  • Drugs and medications 5
  • Insect stings 6
  • Contact with chemicals and irritants 5
  • Physical stimuli 5
  • Contrast media, vaccination, and latex 6
• Many cases remain idiopathic (no identifiable cause) 5

Chronic Urticaria Triggers

• Physical factors account for 5-10% of chronic urticaria cases in children 5
• The causative factor is identified in only about 20% of cases 5
• Approximately one-third of children with chronic urticaria have circulating functional autoantibodies against the high-affinity IgE receptor or against IgE (autoimmune urticaria) 5

Important Clinical Distinctions

Duration-Based Differentiation

• Ordinary urticaria: 2-24 hours per wheal 1
• Contact urticaria: up to 2 hours 1
• Physical urticaria: gone within 1 hour (except delayed pressure urticaria) 1
• Delayed pressure urticaria: 2-6 hours to develop, up to 48 hours to fade 1
• Urticarial vasculitis: weals persist for days 1

Special Considerations in Infants

• Urticaria is not common in newborns and infants since their immune system is functionally insufficient 2
• Careful morphological examination is essential to differentiate acute urticaria from other skin eruptions with overlapping features 2

Differential Diagnosis Considerations

A broad differential diagnosis should be considered, particularly when systemic complaints accompany urticaria 3:

• Chronic spontaneous urticaria 3
• Chronic inducible urticaria 3
• Serum sickness-like reaction 3
• Urticarial vasculitis 3
• Mast cell disorders 3
• Autoinflammatory syndromes (cryopyrinopathies, hyper IgD syndrome, PFAPA, TRAPS, Schnitzler syndrome) 3
• Systemic-onset juvenile idiopathic arthritis 6
• Mastocytosis 6
• Bradykinin-mediated angioedema 6

Red Flags Requiring Further Investigation

• Weals persisting beyond 24 hours suggest urticarial vasculitis 1
• Presence of pyrexia and malaise with spontaneous weals may indicate autoinflammatory syndromes 1
• Systemic symptoms warrant evaluation for underlying systemic diseases (collagenopathies, endocrinopathies, tumors, hemolytic diseases, celiac disease) 5

Treatment Approach

First-Line Treatment

• Second-generation H1 antihistamines are the first-line treatment for urticaria in children 5, 2
• Only antihistamines with proven efficacy and safety should be used in newborns and infants 2
• Fexofenadine is FDA-approved for children aged 6 months and older for chronic idiopathic urticaria, with safety established at doses of 15-30 mg twice daily 7

Additional Therapies

• Short-term corticosteroids may be added in severe cases when antihistamines are ineffective 5, 2, 4
• Anti-H2 antihistamines can be added to anti-H1 antihistamines, though benefits are unclear 5
• Antileukotrienes may benefit a small subgroup of patients with chronic urticaria 5

Refractory Chronic Urticaria

• Omalizumab is FDA-approved for chronic spontaneous urticaria in patients aged 12 years and older who remain symptomatic despite H1 antihistamine treatment 8
• For treatment-resistant cases, cyclosporine and tacrolimus have been used successfully 5

Emergency Management

• When urticaria is associated with anaphylaxis, intramuscular epinephrine must be used immediately, together with antihistamines and steroids (plus fluids and bronchodilators if required) 5

Diagnostic Approach

History-Guided Investigation

• The diagnosis of urticaria is primarily clinical 1
• Investigations should be guided by history and not performed routinely in all patients 1
• Spend time documenting detailed personal history, as different clinical features guide the diagnostic work-up 5

Acute/Episodic Urticaria

• No investigations are required except where suggested by history 1
• IgE-mediated reactions can be confirmed by skin-prick testing and CAP fluoroimmunoassay when environmental allergens are suspected 1
• Results must be interpreted in clinical context 1

Chronic Urticaria

• No investigations required for mild disease responding to H1 antihistamines 1
• For nonresponders with severe disease, useful screening includes:
  • Full blood count and white cell differential (to detect eosinophilia from helminth infections or leukopenia from systemic lupus erythematosus) 1
  • Erythrocyte sedimentation rate (usually normal in chronic ordinary urticaria but raised in urticarial vasculitis and autoinflammatory syndromes) 1
  • Thyroid autoantibodies and thyroid function tests, especially if autoimmune etiology is suspected 1
• Autologous serum skin test (ASST) offers a reasonably sensitive and specific screening test for histamine-releasing autoantibodies in experienced centers 1

Inducible Urticaria

• Specific provocation tests are used to diagnose chronic inducible urticaria, similar to tests used in adults 6
• Important to diagnose appropriately to reduce risk of severe reactions 6