Urticaria

  • Urticaria (Acute <6w, Chronic >6w)
    • Intensely pruritic, well-circumscribed, raised wheals ranging from several millimeters to several centimeters or larger in size
    • Usually benign and self-limited
    • Rule out anaphylaxis
    • Consider rule out significant underlying disease
      • Hashimoto thyroiditis, mastocytosis, systemic lupus erythematosus, Sjögren syndrome, rheumatoid arthritis, vasculitis (see third picture)
  • Angioedema
    • Localized nonpitting edema of the subcutaneous or interstitial tissue that may be painful and warm
  • Causes
    • Immunoglobulin E (IgE) mediated
      • Aeroallergens
      • Contact allergen
      • Food allergens
      • Insect venom
      • Medications
      • Parasitic infections
    • Non-IgE immunologically mediated
      • Aeroallergens (proteases)
      • Autoimmune disease
      • Bacterial infections
      • Cryoglobulinemia
      • Fungal infections
      • Lymphoma
      • Vasculitis
      • Viral infections
    • Nonimmunologically mediated
      • Contact allergen
      • Elevation of core body temperature
      • Food pseudoallergens
      • Light
      • Mastocytosis
      • Medications (direct mast cell degranulation)
      • Physical stimuli (cold, heat, pressure, vibration)
      • Water
  • History
    • Onset, timing (e.g., with the menstrual cycle, if an association is suspected), location, and severity of symptoms; associated symptoms, which may suggest anaphylaxis;
    • Potential environmental triggers.
    • Medication (especially new or recently changed dosages)
    • Allergies
    • Recent infections, travel history
    • Family history of urticaria and angioedema
    • Review of systems, r/o systemic illnesses
      • Vasculitis - fever, arthralgias, arthritis, weight changes, bone pain, or lymphadenopathy
    • Sexual history, illicit drug use, transfusion history (viral hepatitis and human immunodeficiency virus)
  • Physical Exam
    • Vital signs
    • Cardiopulmonary examination, r/o anaphylaxis and infectious causes
    • Skin Exam
    • Testing for dermatographism (i.e., urticaria that appears in the pattern of localized pressure elicited by stroking with the blunt end of a pen or tongue blade)
  • Investigation (usually unnecessary)
    • Consider CBC, ESR/CRP, TSH, UA, LFTs
    • Consider r/o vasculitis with biopsy if >24h , painful, residual purpura/hyperpigmentation
  • Management
    • Epinephrine IM and airway management if anaphylaxis or angioedema of airway
    • Identify and avoid trigger
    • Avoid aspirin/NSAIDs, alcohol, wearing tight clothing
    • Second-generation H1 antihistamines
      • Loratadine (Claritin) 10mg PO daily, desloratadine (Clarinex), fexofenadine (Allegra), cetirizine (Zyrtec), and levocetirizine (Xyzal)
      • Can titrate to 2-4 times normal dose (or use first-gen H1 antihistamines)
    • Consider adding H2 antihistamines
      • Cimetidine (Tagamet), famotidine (Pepcid), and ranitidine (Zantac)
    • Consider in severe or angioedema, prednisone (0.5 to 1 mg per kg per day) x 3-10 days
    • Prescribe epinephrine autoinjectors if risk of anaphylaxis