Hives

Hives (Urticaria)

Definition
Hives, also known as urticaria, are raised, red or skin-colored welts (wheals) on the skin surface that appear suddenly and cause itching, burning, or stinging. They can be acute (lasting less than 6 weeks) or chronic (lasting more than 6 weeks).

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Causes and Pathophysiology

Hives occur due to the release of histamine and other inflammatory mediators from mast cells in the skin, leading to vasodilation, increased capillary permeability, and edema. Common causes include:

• Allergic reactions: Foods (nuts, shellfish, eggs, milk, strawberries, tomatoes), medications (penicillin, sulfonamides, NSAIDs, aspirin), insect stings, latex.

• Infections: Viral (common cold, hepatitis), bacterial (streptococcus, Helicobacter pylori), parasitic infestations.

• Physical triggers: Cold, heat, pressure, vibration, exercise, sunlight (physical urticaria).

• Chronic conditions: Thyroid disease, autoimmune disorders, systemic lupus erythematosus.

• Idiopathic: In about 50% of chronic urticaria cases, no cause is identified.

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Clinical Features

• Skin lesions:

  • Raised, itchy welts with pale centers and red surrounding flares.

  • Size varies (millimeters to several centimeters).

  • Lesions typically last <24 hours but may recur in waves.

• Angioedema: Deeper swelling of the lips, eyelids, hands, feet, or genitals may accompany hives.

• Symptoms:

  • Severe itching (worse at night).

  • Burning or stinging sensations.

  • In some cases, shortness of breath or throat tightness (emergency – risk of anaphylaxis).

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Diagnosis

• History and examination: Timing, triggers, duration, associated swelling, systemic symptoms.

• Laboratory tests (if chronic or severe): CBC, ESR/CRP, thyroid antibodies, ANA, stool for parasites, allergy testing (skin prick or IgE testing).

• Provocation tests: Ice cube test for cold urticaria, exercise test for cholinergic urticaria.

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Management

1. General Measures

• Avoid identified triggers (allergens, heat, pressure, tight clothing, alcohol, NSAIDs).

• Keep skin cool, wear loose cotton clothing.

• Stress management (stress worsens urticaria).

2. Pharmacological Treatment

• First-line: Non-sedating H1 antihistamines

  • Cetirizine 10 mg once daily

  • Loratadine 10 mg once daily

  • Fexofenadine 180 mg once daily

• If symptoms persist:

  • Increase dose (up to 4 times daily under supervision).

  • Add sedating antihistamines at night (Hydroxyzine 25 mg or Diphenhydramine 25–50 mg).

  • Add H2 antihistamines (Ranitidine, Famotidine) as adjuncts.

• Severe acute attacks:

  • Oral corticosteroids (Prednisolone 30–40 mg daily, tapered over 5–7 days).

  • Epinephrine (0.3–0.5 mg IM) in case of associated anaphylaxis.

• Chronic/refractory cases:

  • Leukotriene receptor antagonists (Montelukast 10 mg daily).

  • Omalizumab (anti-IgE monoclonal antibody) for chronic spontaneous urticaria.

  • Cyclosporine, Methotrexate, or Mycophenolate mofetil in resistant autoimmune urticaria.

3. Pediatric Considerations

• Children often present with acute urticaria post-viral infection or after food exposure.

• Use weight-adjusted non-sedating antihistamines.

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Complications

• Anaphylaxis (life-threatening, requires epinephrine).

• Sleep disturbance, anxiety, and reduced quality of life due to chronic itch.

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Precautions

• Patients with recurrent angioedema or airway symptoms should carry an epinephrine auto-injector.

• Chronic urticaria >6 weeks should be investigated for underlying autoimmune or systemic disease.

• Avoid excessive steroid use; rely mainly on antihistamines for long-term control.

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Drug Interactions

• Antihistamines may interact with alcohol and sedatives (increased drowsiness).

• Loratadine and cetirizine have minimal interactions but can interact with strong CYP3A4 inhibitors (e.g., ketoconazole, erythromycin).

• Montelukast may interact with phenobarbital or rifampin (reduced effect).

• Cyclosporine interacts with nephrotoxic and hepatotoxic drugs (aminoglycosides, NSAIDs).