Urticaria

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Description

  • Urticaria: an inflammatory skin disorder characterized by hives with or without angioedema
  • Urticaria can be classified as acute or chronic.
    • Acute: recurring lesions that persist for <6 weeks
    • Chronic: recurring lesions that persist for >6 weeks
  • The causes of urticaria vary; acute urticaria is often self-limited and trigger may not be identifiable. In chronic urticaria, further allergen testing may be warranted.
  • Presentation: a cutaneous lesion or lesions involving edema of the epidermis and/or dermis presenting with rapid onset and pruritus; individual lesions will change over minutes to hours with no individual lesions persisting >24 hours without change
  • Etiology of urticaria is either spontaneous or induced.
  • System(s) affected: integumentary
  • Synonym(s): hives; wheals

Epidemiology

Urticaria may be spontaneous or induced.

Incidence

  • The peak onset happens around 20 to 40 years of age, and affects women more frequently than men. However, urticaria can also affect children, adult, and geriatric population to similar extent.
  • Chronic urticaria is also associated with autoimmune disorders and prevalence increase with variety of chronic infections.
  • In 20% of patients, chronic urticaria lasts >10 years.

Prevalence

  • It is a common disorder that occurs in 15–25% of individuals some point in their lives.
  • Up to 36% of patients with acute urticaria can progress to CSU.
  • The prevalence of CSU is about 0.12–0.30% for adult and children

Etiology and Pathophysiology

  • Core mechanism
    • Mast-cell activation (IgE-dependent, autoimmune IgG binding to IgE docking site, or non-IgE “pseudoallergic” triggers) → rapid degranulation of histamine, leukotrienes, cytokines, proteases
    • Mediator release in superficial dermis → transient wheals; in deep dermis/subcutis → angioedema
  • Trigger categories
    • Acute spontaneous urticaria (ASU)
      • Viral and bacterial infections
      • IgE mediated food allergy (peanuts, seafood, eggs, etc.); pseudoallergenic foods such as strawberries, tomatoes, preservatives, and coloring agents contain histamine.
      • Drugs: IgE-mediated (e.g., penicillin and other antibiotics), direct mast cell stimulation (e.g., aspirin, NSAIDs, opiates)
      • Others: inhalant, contact, ingestion, or occupational exposure (e.g., latex, cosmetics)
      • Transfusion reaction
    • Chronic spontaneous urticaria (CSU)
      • Autoimmune thyroid disease, other auto-antibodies
      • Indolent infections (Helicobacter pylori, parasites)
      • Chronic meds (NSAIDs, ACE-I, hormones)
      • Hormonal shifts (pregnancy, progesterone)
      • Collagen-vascular disease, malignancy
  • Chronic inducible urticaria (CIU)
  • Physical stimuli
    • Dermographism (most common)
    • Cold, heat, solar/UV, delayed pressure, vibration
    • Cholinergic (exercise, emotion, hot bath)
    • Contact (latex, chemicals)
    • Aquagenic (water)

Genetics

No consistent pattern known: Chronic urticaria displays an autoimmune-like genetic signature with HLA-B44 and vitamin D receptor variants being susceptible markers.

Risk Factors

Chronic urticaria

  • Female sex
  • Obesity with BMI ≥30 kg/m2
  • Autoimmune thyroid disease
  • NSAIDs sensitivity
  • Psychological stress
  • H. pylori

General Prevention

Avoidance of known triggers is the mainstay of prevention.

Commonly Associated Conditions

  • Autoimmune thyroid disease
  • Atopic dermatitis/allergic rhinitis
  • Anxiety and depression
  • Angioedema (common)
  • Anaphylaxis (somewhat common)

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