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Urticaria

Specialties > Child health

Background knowledge 🧠

Definition

  • Urticaria, also known as hives, is a common skin condition characterised by the rapid onset of itchy wheals (raised, red or white areas on the skin) that usually resolve within 24 hours.
  • It may be acute (lasting less than 6 weeks) or chronic (lasting 6 weeks or more).

Epidemiology

  • Affects approximately 20% of people at some point in their lives.
  • More common in adults, particularly females.
  • Chronic urticaria affects about 1% of the population.
  • Often associated with other atopic conditions like asthma and eczema.

Aetiology and Pathophysiology

  • Mediated by the release of histamine and other inflammatory mediators from mast cells and basophils in the skin.
  • Triggers include infections, medications (e.g., NSAIDs, antibiotics), food allergens, insect stings, and physical factors (e.g., pressure, temperature changes).
  • Autoimmune mechanisms are involved in some cases, particularly chronic urticaria.
  • Stress can exacerbate the condition.

Types

  • Acute Urticaria: Lasts less than 6 weeks, often due to infections, medications, or food allergies.
  • Chronic Spontaneous Urticaria (CSU): Lasts 6 weeks or more, often idiopathic.
  • Chronic Inducible Urticaria: Triggered by specific physical stimuli (e.g., cold, pressure, sunlight).
  • Angioedema: Similar to urticaria but involves deeper swelling of the skin and mucous membranes.

Clinical Features 🌡️

Symptoms

  • Itchy wheals (hives) that appear suddenly and may change shape and size.
  • Wheals may appear anywhere on the body.
  • Associated with burning or stinging sensation.
  • Worsened by scratching.
  • Angioedema: Swelling, particularly around the eyes, lips, and sometimes the throat, causing discomfort or difficulty breathing.

Signs

  • Erythematous, edematous, well-defined wheals on the skin.
  • Wheals typically blanch with pressure.
  • Angioedema: Non-pitting swelling, often around the eyes and lips.
  • Dermatographism: Stroking the skin can cause wheals to appear.

Investigations 🧪

Tests

  • Primarily clinical diagnosis based on history and examination.
  • Consider full blood count (FBC) and C-reactive protein (CRP) to rule out systemic causes.
  • Allergy testing may be useful in acute urticaria with a suspected allergen.
  • Autoimmune screening (e.g., thyroid antibodies) in chronic cases.
  • Skin biopsy if vasculitis or other differential diagnoses are considered.

Management 🥼

Management

  • Avoidance of known triggers (e.g., specific foods, medications).
  • Antihistamines (H1 blockers) are first-line treatment.
  • Second-line: Increase antihistamine dose or add H2 blockers (e.g., ranitidine) or leukotriene receptor antagonists.
  • Severe cases: Short course of oral corticosteroids.
  • Chronic cases: May require long-term antihistamine use and specialist referral.
  • Consider omalizumab for refractory chronic urticaria.
  • Angioedema with airway involvement: Emergency treatment with adrenaline, oxygen, and corticosteroids.

Complications

  • Chronic urticaria can significantly impact quality of life.
  • Risk of anaphylaxis if associated with angioedema.
  • Side effects from long-term antihistamine or corticosteroid use.
  • Psychological impact, including anxiety and depression.

Prognosis

  • Acute urticaria often resolves within days to weeks.
  • Chronic urticaria may persist for months or years but may eventually resolve spontaneously.
  • Regular follow-up is essential for chronic cases.

Key Points

  • Urticaria is common and often self-limiting.
  • Consider a broad differential diagnosis.
  • Management focuses on symptom control and avoiding triggers.
  • Chronic cases require specialist input.
  • Educate patients about potential triggers and treatment options.

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Child health