Supplementary Figure Legend Supplementary Figure 1. Study flowchart. CSU, chronic spontaneous urticaria; GA, general anaesthesia 1urticaria codes: L50.1, L50.8, and L50.9 Supplementary Figure 2. Test of Cox proportional hazard model assumption (P=0.550), suggesting no significant deviation from proportionality. Supplementary Figure 3. Cumulative incidence of chronic spontaneous urticaria among different age groups in general anaesthesia-exposed and unexposed cohorts. (a) 0-19 years, (b) 20-39 years, (c) 40-59 years, and (d) ≥ 60 years. Supplementary Figure 4. Clinical features of chronic spontaneous urticaria in exposed and unexposed participants. (a) Proportion of chronic spontaneous urticaria patients according to disease duration. (b) Proportion of chronic spontaneous urticaria patients according to the frequency of steroid or immunosuppressant use during the follow-up periods.