Urticaria

Urticaria is a topic covered in the 5-Minute Emergency Consult.

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Basics

Description

  • Cutaneous mast and basophil cellular release of inflammatory mediators, primarily histamine:
    • Increased vascular permeability and pruritus
  • Edema of the epidermis as well as the upper and middle dermis:
    • More common in children and young adults
    • More common in women
    • More common in the atopic patient
  • 40% of patients with urticaria will have a component of angioedema:
    • Affects deeper subdermal and/or submucosal sites

Pediatric Considerations
  • Urticaria is often the result of reactions to foods and infections
  • Swelling of distal extremities and acrocyanosis may be prominent in infants
  • Bullae may form in the center of the wheal, especially on legs and buttocks

Etiology

Acute:
Presumptive trigger may be found, but majority of cases are idiopathic
Course of <6 wk
  • Drugs:
    • Few have recurrent urticaria on later antigenic challenge
  • Foods or additives
  • Herbal medications, vaccines, opiates
  • Insect bites and stings
  • Connective tissue diseases
  • Endocrine disorders, especially Hashimoto's thyroiditis
  • Cancers, especially lymphoproliferative
  • Hormonal imbalance, pregnancy, menstrual cycle, exogenous estrogens
  • Infections:
    • Viral (including hepatitis, HIV)
    • Viral URI most common associated infection
    • Bacterial
    • Fungal
    • Parasitic
  • Inhaled or contact allergen
  • Emotional stress
  • Physical urticaria—>20 identified types, including:
    • Dermographism:
      • Most common physical form
      • Reaction to skin pressure
      • Linear wheals under tight clothing
      • Areas scratched with a firm object
    • Cholinergic:
      • Monomorphic wheals 2–3 mm
      • Bright red flare and intense pruritus
    • A response to elevated core temperature:
      • Hot bath
      • Fever
      • Exercise
    • Other rare forms:
      • Cold-induced (may be fatal in cold immersions)
      • Sun exposure
      • Aquagenic
Chronic:
Course of >6 wk
  • 75% idiopathic in nature
  • Autoimmune disease spectrum
  • Immune complex–induced
  • Often an unrecognized recurring physical urticaria
  • May be due to occult or subclinical infection or systemic disease

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Basics

Description

  • Cutaneous mast and basophil cellular release of inflammatory mediators, primarily histamine:
    • Increased vascular permeability and pruritus
  • Edema of the epidermis as well as the upper and middle dermis:
    • More common in children and young adults
    • More common in women
    • More common in the atopic patient
  • 40% of patients with urticaria will have a component of angioedema:
    • Affects deeper subdermal and/or submucosal sites

Pediatric Considerations
  • Urticaria is often the result of reactions to foods and infections
  • Swelling of distal extremities and acrocyanosis may be prominent in infants
  • Bullae may form in the center of the wheal, especially on legs and buttocks

Etiology

Acute:
Presumptive trigger may be found, but majority of cases are idiopathic
Course of <6 wk
  • Drugs:
    • Few have recurrent urticaria on later antigenic challenge
  • Foods or additives
  • Herbal medications, vaccines, opiates
  • Insect bites and stings
  • Connective tissue diseases
  • Endocrine disorders, especially Hashimoto's thyroiditis
  • Cancers, especially lymphoproliferative
  • Hormonal imbalance, pregnancy, menstrual cycle, exogenous estrogens
  • Infections:
    • Viral (including hepatitis, HIV)
    • Viral URI most common associated infection
    • Bacterial
    • Fungal
    • Parasitic
  • Inhaled or contact allergen
  • Emotional stress
  • Physical urticaria—>20 identified types, including:
    • Dermographism:
      • Most common physical form
      • Reaction to skin pressure
      • Linear wheals under tight clothing
      • Areas scratched with a firm object
    • Cholinergic:
      • Monomorphic wheals 2–3 mm
      • Bright red flare and intense pruritus
    • A response to elevated core temperature:
      • Hot bath
      • Fever
      • Exercise
    • Other rare forms:
      • Cold-induced (may be fatal in cold immersions)
      • Sun exposure
      • Aquagenic
Chronic:
Course of >6 wk
  • 75% idiopathic in nature
  • Autoimmune disease spectrum
  • Immune complex–induced
  • Often an unrecognized recurring physical urticaria
  • May be due to occult or subclinical infection or systemic disease

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