The definition of CSU and classification of chronic urticaria.


CSU is defined as the spontaneous appearance of wheals, angioedema or both, lasting for more than 6 weeks. The cause is unknown.

Urticaria may be classified into different subtypes based on duration and cause:

Classifying chronic urticaria1

Diagram detailing the classification of chronic spontaneous urticaria and chronic inducible urticaria by symptom duration and triggers

Adapted from Zuberbier T et al. 2018.1



  1. Zuberbier T et al. Allergy 2018;73(7):1393–1414.
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XSU20-C014 July 2020.

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