Objectives@#. In this study, we evaluated the associations between birth-related exposures, postnatal factors, and the risk of allergic rhinitis and asthma in children and adolescents. @*Methods@#. We performed a comprehensive search of five literature databases up to May 2023. To quantify the associations of birth-related exposures (birth weight, delivery mode, prematurity, sex, maternal age, and parental allergy history) and postnatal factors (birth order, number of siblings, breastfeeding exclusivity, and breastfeeding duration) with allergic disease, we calculated pooled odds ratios and 95% confidence intervals. We conducted subgroup analyses for allergic disease type, birth order, number of siblings, and parental allergy history. The methodological quality of the identified studies was evaluated using the Newcastle-Ottawa Scale. @*Results@#. This meta-analysis included 31 studies, encompassing 218,899 patients in total. The birth-related exposures of low birth weight, maternal age, and prematurity (less than 37 weeks gestation) were not significantly associated with the risk of asthma or allergic rhinitis during childhood or adolescence. Male sex, family history of allergy, and cesarean delivery were linked to an elevated risk of asthma or allergic rhinitis. Among postnatal factors, exclusive breastfeeding, breastfeeding for longer than 6 months, second or later birth order, and having siblings exhibited protective effects against allergic diseases in offspring. @*Conclusion@#. The risks of allergic rhinitis and asthma were elevated in male patients, those delivered by cesarean section, and those with a family history of allergy. Conversely, exclusive breastfeeding, breastfeeding for longer than 6 months, and having siblings corresponded to a reduced risk of respiratory allergic diseases.