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 (see second picture)

• 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

  • Pain

  • Asociated 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 (eg. 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

• May consider

  • r/o Vasculitis with biopsy if >24h , painful, residual purpura/hyperpigmentation

  • r/o Hereditary Angioedema with C1 esterase inhibitor (level and function), C4

  • r/o Mastocytosis/anaphylaxis with Tryptase

Management

• Epinephrine IM and airway management if anaphylaxis or angioedema of airway

  • Prescribe epinephrine autoinjectors if risk of anaphylaxis

• Identify and avoid trigger

• Avoid aspirin/NSAIDs, alcohol, wearing tight clothing 

• Second-generation H1 antihistamines

  • Cetirizine (Reactine) 10mg PO daily,  loratadine (Claritin) 10mg PO daily, desloratadine (Clarinex), fexofenadine (Allegra), and levocetirizine (Xyzal)

    • Can increase weekly up to 4 times normal dose, eg. Ceterizine 40mg qHS

• May Consider adding H2 antihistamines 

  • Cimetidine (Tagamet), famotidine (Pepcid), and ranitidine (Zantac)

• May Consider in severe or angioedema, prednisone (0.5 to 1 mg per kg per day up to 50mg/d) x 3-5 days

• Refer to dermatologist or allergist if systemic symptoms, or symptoms >2-4 weeks of optimized treatment or diagnosis uncertain

  • Second-line therapies include omalizumab, cyclosporine, dupilumab