Acute Urticaria

Authors: Cathleen Collins, MD and Kathleen Luskin, MD

Editor: Kathleen Luskin, MD

Definition: Urticarial rash occurring for less than 6 weeks; versus chronic urticaria, in which rash has occurred for more than 6 continuous weeks [1]. Lesions appear identical between acute and chronic urticaria, so differentiation between the two at onset is not feasible [2].

- Common: lifetime prevalence of about 20% [3, 4]

- Most cases resolve within 1 week, < 40% become chronic [5]

- High prevalence in pediatrics [5]

Diagnosis:

- Clinical: based on clinical signs & symptoms

• Wheal: well-circumscribed central swelling (variable size, shape) typically surrounded by erythema; pruritis more common than burning. Each individual lesion lasts < 24 hours and heals without residual scar, bruise or dyspigmentation (unless there is trauma related to scratching) [4]

• Can be associated with swelling/angioedema (deep swelling in lower dermis and subcutaneous tissues that may be more tingling, burning or tight rather than itchy; resolution usually within 72 hours); occasionally, angioedema may occur alone [4]

• Improvement with anti-histamines is typical