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Urticaria, commonly known as hives, is characterized by the episodic appearance of pruritic, erythematous papules, or plaques with superficial swelling of the dermis. Angioedema often coexists with urticaria and results from a deeper swelling of the dermis, subcutaneous, or submucosal tissue. Urticaria is classified as either acute or chronic based on symptom duration of less than 6 weeks or more than 6 weeks, respectively. Chronic urticaria, defined by symptom duration of greater than 6 weeks, can be further classified as chronic inducible urticaria (CIndU) or chronic spontaneous urticaria (CSU). CIndU is comprised of many subtypes in which a specific trigger can quickly induce hives, while the majority of hives in CSU do not occur as a result of a known trigger. Therapy is based on reducing pruritus and lesion severity and includes trigger avoidance where applicable. In the authors’ experience, therapy is usually initiated with H1 antihistamines; omalizumab is often first-line systemic therapy for antihistamine-refractory cases while immunosuppressants are usually reserved for recalcitrant cases. See Table 26-1.
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