Chronic spontaneous urticaria (CSU) is defined by the presence of recurrent urticaria (also called hives or wheals), angioedema, or both, for a period of six weeks or longer. Associated angioedema occurs in approximately one-half of patients with CSU and usually affects the lips, cheeks, periorbital areas of the face, extremities, and genitals. [1]
Think about it in steps. Steps range from 1 to 4.
[1] D Khan. Chronic spontaneous urticaria: Standard management and patient education. Uptodate
[2] D Khan. Chronic spontaneous urticaria: Treatment of refractory symptoms. Uptodate
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