• Diagnosis is based on patient’s history and physical examination

• Urticaria is classified as acute or chronic, and as spontaneous (no triggering factor) or inducible (a particular triggering factor is identified)
  • A specific cause is more likely to be identified in acute cases
•  Can be triggered by immunological or non-immunological mechanism

Acute Urticaria

• Lesions occurring ≤6 weeks in duration and usually without angioedema
• More common in children and young adults and tends to have a triggering event
• Routine laboratory work-ups are not required, except when the cause of the urticaria points to a type I food hypersensitivity or other triggering factors like medications [eg non-steroidal anti-inflammatory drugs (NSAIDs)]

Chronic Urticaria

• More common in adults (3rd and 4th decades of life), symptoms last >6 weeks

Chronic Spontaneous Urticaria

• Presence of wheals, angioedema or both for >6 weeks due to factors that are identifiable or idiopathic

Inducible Urticaria

• Cold urticaria
• Delayed pressure urticaria
• Heat urticaria
• Symptomatic dermographism
  • Daily lesions and recurrent episodic lesions are not differentiated
• Solar urticaria
• Vibratory angioedema
• Aquagenic urticaria
• Cholinergic urticaria
• Contact urticaria

Autoimmune Chronic Spontaneous Urticaria (ACU)

• Proposed gold standard for diagnosis of ACU (combination of all 3 parameters):
  • Positive bioassay [eg basophil histamine release assay (BHRA), basophil activation marker expression] AND
  • Positive autoreactivity [eg positive autologous serum skin test (ASST)] AND
  • Positive immunoassay for specific IgG autoantibodies against FcεRIα and/or anti-IgE

Look for typical lesions of urticaria

• Wheals which typically are fleeting, lasting within 30 minutes-24 hours, have a central swelling of variable size surrounded by erythema and associated with itching, sometimes burning sensation
• Angioedema characterized by a sudden evident swelling of the lower dermis and subcutis or mucous membranes, that is sometimes painful which may last up to 72 hours
• Lesions may appear on any part of the body

Stroke the arm to test for dermographism/dermatographism

• Discontinue antihistamine therapy for at least 2-3 days, immunosuppressive therapy for at least a week

Chronic Urticaria

• Diagnostic examinations are based on the patient’s history and physical examination

Chronic Spontaneous Urticaria

• Consider other possible diagnoses in patients with presentations indicative of chronic urticaria
• Further tests are requested if indicated by the patient’s history and physical examination, most notably in patients with chronic and/or on-and-off disease presentation
• Assess disease activity of chronic spontaneous urticaria
  • Several guidelines recommend using the Urticaria Activity Score (UAS7) system in assessing disease severity and treatment effectivity
  • Summation of scores of symptoms during a 7-day period
    • 0 = no wheals, no pruritus
    • 1 = mild wheals (<20 wheals within 24 hours) + mild (nontroublesome) pruritus 
    • 2 = moderate wheals (20-50 wheals within 24 hours) + moderate (troublesome but does not interfere with daily activities or sleep) pruritus 
    • 3 = intense wheals (>50 wheals within 24 hours or large confluent wheals) + intense (severely troublesome, interferes with daily activities and sleep) pruritus

Chronic Inducible Urticaria

• Provocation threshold measurements are used to assess disease activity, while the urticaria control test (UCT) is used to determine how well the disease is prevented from recurring