Data extraction
From each eligible study, we recorded information about first author, publication year, journal, population characteristics, total and per-arm sample size, treatment indication, omalizumab and comparator dose, mode of administration and study duration. Moreover, we extracted information on rhinitis-related outcomes along with their effect estimates. Standardized mean differences (with the corresponding standard errors) were calculated for the continuous outcomes (Daily Symptom Severity Score, DSSS; Daily Nasal Symptom Severity Score, DNSSS; Daily Ocular Symptom Severity Score, DOSSS; Rescue Medication, RM; Rhino-conjunctivitis Quality of Life Questionnaire, RQoL) and Relative Risks (RRs) along with their Confidence Intervals (CIs) were calculated for Adverse Events (AE) that were assessed as binary outcomes. Concerning the methodological features of the included studies, we extracted information on randomization mode, allocation concealment and blinding.