[National Consensus on the Diagnosis and Treatment of Chronic Urticaria (2025). Part I: Definition, classification, and diagnosis].

Urticaria is a condition characterized by the presence of pruritic wheals and/or angioedema, and is classified according to its duration as acute (less than or equal to 6 weeks) and chronic (CU) (greater than 6 weeks). Chronic urticaria is subdivided into chronic spontaneous urticaria (CSU) and chronic inducible urticaria (CIndU), depending on the presence or absence of a defined stimulus. The predominant form is CSU, affecting more than 75% of patients. Despite this, in some cases, both types of CU may coexist. The lifetime prevalence of CU is approximately 1%, with a 2:1 ratio of women predominating. The maximum incidence is observed between 20 and 40 years of age, being most of the time self-limited, with a duration between 1 to 5 years, although in up to 20% of patients it can last longer, generating great affectation in the quality of life, academic and/or work performance. The diagnosis of CU is clinical, based on the patient's history and physical examination. Laboratory tests are requested based on the patient's clinical history, and extensive laboratory tests are most often unnecessary. To date, there are no curative treatments for this pathology, and treatment is based on the use of 2nd generation antihistamines, the dose of which can be quadrupled according to response. In patients who are refractory to antihistamines, systemic treatments such as omalizumab, a monoclonal antibody that must be indicated by a specialist, is suggested. The national consensus on the diagnosis and treatment of chronic urticaria is presented below, comprising Parts I and II. The objective of this consensus is to review the diagnostic and therapeutic recommendations for CU based on the experience of expert dermatologist and immunologists belonging to the respective Chilean scientific societies, in relation to the available guidelines and evidence.