Abstract Background Chronic spontaneous urticaria (CSU) formerly known as chronic idiopathic urticaria (CIU) is a severe and distressing skin condition that remains uncontrolled in approximately one half of patients, despite the use of licensed, recommended doses of modern, second-generation H 1 -antihistamines. So far, the humanistic, societal and economic burden of CSU/CIU has not been well quantified. Therefore it is important to broaden our understanding of how CSU/CIU impacts patients, society, and healthcare systems, by determining the disease burden of CSU/CIU and the associated unmet need; as well as to further guide the use of new treatments in an efficient and cost-effective manner. Methods ASSURE-CSU is an observational, multicenter study being conducted in the UK, Germany, Canada, France, Italy, Spain, and The Netherlands. The study comprises a retrospective medical chart review in conjunction with patient surveys (including validated tools for assessment of disease impact) and an 8-day patient diary. The primary objectives of the study are to describe patient demographics, medical history, treatments, and healthcare resource utilization based on medical-record data and to assess the impact of disease, healthcare resource utilization, work days missed, and productivity loss based on patient-reported data. Approximately 700 patients (aged ≥18 years) will be enrolled who have CSU/CIU despite currently receiving treatment, and have had persistent symptoms for at least 12 months. Data will be collected retrospectively for the 12 months (±1 month) prior to enrolment wherever possible, and prospectively for the week following enrolment. Discussion ASSURE-CSU will be the first study to examine the economic and humanistic burden of disease in patients diagnosed with CSU/CIU who are symptomatic despite treatment. By combining retrospective evaluation of medical records with prospective patient surveys and 8-day diaries, across seven different countries, the ASSURE-CSU study will contribute to a better understanding and acknowledgement of the burden of disease in patients with symptomatic chronic spontaneous .