Chronic Urticaria: Advances in Understanding of the Disease and Clinical Management.

Chronic urticaria (CU) is a common skin condition characterized by the recurrence of wheals, with or without angioedema, which lasts for at least 6 weeks. Owing to its pruritus and incurability, this disease adversely affects the patients' physical and mental health and diminishes the quality of life. CU is generally classified into two subtypes based on the relevance of eliciting factors: chronic spontaneous urticaria (CSU) and chronic inducible urticaria (CIndU), the latter of which is further divided into several subtypes. To improve the understanding and clinical management of this highly heterogeneous disorder, the EAACI/GA2LEN/EDF/WAO guideline was developed and published in 2018 based on evidence and expert consensus. The diagnostic and treatment algorithms proposed by the guideline have largely facilitated dermatologists in clinical practice. However, several questions remained unsolved and have been widely investigated in the recent years. First, a better understanding of the association between chronic urticaria and its potential underlying causes or eliciting factors such as autoimmunity, infections, coagulation aberrance, and vitamin D deficiency is warranted. This would lead to updates in the diagnostic and treatment procedures of different subtypes of chronic urticaria. Secondly, treatment for recalcitrant cases, especially those resistant to or intolerant of second-generation antihistamines and (or) omalizumab, calls for novel therapeutic measures or strategies. In the present review, we summarized recent advances in the understanding and management of both CSU and CIndU, with special emphasis on their underlying causes or eliciting factors, pathogenic mechanisms, potential targets for intervention, and advances in treatment strategies.