What is the appropriate workup and treatment for a patient presenting with hives (urticaria)?

Workup and Management of Urticaria (Hives)

The most appropriate workup for urticaria (hives) should focus on identifying potential triggers while initiating prompt treatment with non-sedating H1 antihistamines as first-line therapy, which can be increased above the licensed dose if necessary for symptom control. 1

Clinical Classification

• Urticaria can usually be classified based on clinical presentation without extensive investigation 1
• Acute urticaria: duration less than 6 weeks 2
• Chronic urticaria: duration more than 6 weeks 2
• Physical urticaria: weals typically last less than 1 hour (except delayed pressure urticaria) 1
• Ordinary urticaria: weals typically last 2-24 hours 1
• Urticarial vasculitis: should be suspected if weals last longer than 24 hours (confirm with skin biopsy) 1

Initial Evaluation

• Assess severity of urticaria using a standardized approach:
  • Mild: less than 3 hives 1
  • Moderate: 3-10 hives 1
  • Severe: generalized involvement 1
• Evaluate for associated angioedema, which occurs in approximately 40% of urticaria cases 2
• Check for signs of anaphylaxis including respiratory symptoms, hypotension, or gastrointestinal symptoms 1
• Identify potential triggers:
  • Foods (particularly in acute urticaria) 2
  • Medications (especially NSAIDs, aspirin, antibiotics) 2
  • Insect stings 3
  • Physical stimuli (cold, heat, pressure, sunlight) 1

Laboratory Testing

• For acute urticaria with clear trigger, extensive testing is usually unnecessary 1
• For chronic urticaria (>6 weeks), consider:
  • Complete blood count
  • Erythrocyte sedimentation rate or C-reactive protein
  • Thyroid function tests (due to association with autoimmune thyroid disease) 2
  • Consider autologous serum skin test (ASST) as a marker for autoimmune urticaria 1
• Skin biopsy is indicated if urticarial vasculitis is suspected (weals lasting >24 hours) 1

Treatment Algorithm

First-Line Treatment

• Non-sedating H1 antihistamines are the mainstay of therapy 4
• Options include:
  • Cetirizine
  • Desloratadine
  • Fexofenadine
  • Levocetirizine
  • Loratadine
  • Mizolastine 1
• Offer patients a choice of at least two non-sedating H1 antihistamines as responses vary between individuals 1

For Inadequate Response

• Increase the dose of non-sedating H1 antihistamines above the licensed recommendation when benefits outweigh risks 1
• Add a sedating antihistamine at night (e.g., chlorphenamine 4-12 mg or hydroxyzine 10-50 mg) to help with sleep disruption 1
• Consider adding an H2 antihistamine (e.g., ranitidine, cimetidine) which may provide better control than H1 antihistamine alone 1, 3
  • A combination of diphenhydramine with ranitidine or cimetidine has shown better efficacy than diphenhydramine alone 5

For Severe or Refractory Cases

• Short courses of oral corticosteroids may be considered for severe acute urticaria (e.g., prednisolone 50 mg daily for 3 days) 1
• Antileukotrienes (e.g., montelukast) may benefit some patients, particularly those with aspirin sensitivity 1
• For chronic autoimmune urticaria unresponsive to conventional treatments, immunomodulating therapies may be considered 1

Special Considerations

Angioedema Management

• If angioedema affects the mouth or airway, prompt treatment is essential 1
• Intramuscular epinephrine can be life-saving in severe laryngeal angioedema 1
• For adults and adolescents >12 years: 0.5 mL of 1:1000 (500 μg) epinephrine intramuscularly 1

Medication Adjustments

• In renal impairment:
  • Avoid acrivastine in moderate renal impairment 1
  • Halve the dose of cetirizine, levocetirizine, and hydroxyzine 1
• In hepatic impairment:
  • Avoid mizolastine, alimemazine, chlorphenamine, and hydroxyzine in severe liver disease 1
• In pregnancy:
  • Avoid antihistamines if possible, especially in first trimester 1
  • If necessary, chlorphenamine has the longest safety record 1

Patient Education and Follow-up

• Provide emergency treatment plan for patients at risk of severe reactions 1
• Consider self-injectable epinephrine prescription for patients with history of severe reactions 1
• Advise patients about possible recurrent urticaria over 1-2 days after acute episodes 1
• For chronic urticaria, schedule follow-up visits to assess treatment response 1

Prognosis

• Approximately 50% of patients with chronic urticaria (weals alone) clear within 6 months 1
• Patients with both weals and angioedema may have a poorer prognosis, with over 50% still having active disease after 5 years 1