<p>Exposure to atmospheric pollutants is associated with the occurrence of various allergic diseases in children. However, evidence regarding the impact of intrauterine mixed exposure to multiple atmospheric pollutants on childhood asthma and allergic rhinitis were scarce. This study examined the relationship between intrauterine mixed exposure to PM₁, PM_2.5, PM₁₀, NO₂, and O₃ and childhood asthma and allergic rhinitis. From November to December 2019, a questionnaire was used to gather data regarding asthma and allergic rhinitis from 7791 children aged 3 to 6&#xa0;years in Wuhan, China. We applied quantile-based g-computation models to assess the relationship between intrauterine mixed exposure to multiple atmospheric pollutants and childhood asthma and allergic rhinitis to identify the key atmospheric pollutants within the mixture. For each quartile increase in mixed exposure concentration, a positive association was observed with childhood asthma (OR = 1.24, 95% CI 1.04, 1.49). Notably, the strongest deleterious effect on asthma incidence was observed among children with breastfeeding duration &lt; 1&#xa0;month (OR = 1.58, 95% CI 1.01, 2.45), while the highest risk for allergic rhinitis occurred in those breastfed for 1–6&#xa0;months (OR = 1.26, 95% CI 1.07, 1.47). PM₁₀ demonstrated the highest positive weight in these models (index weight of 0.59 and 0.67, respectively). Intrauterine mixed exposure to atmospheric pollutants, particularly particulate matter and NO₂, increased childhood asthma and allergic rhinitis risks, suggesting that public health policymakers should strengthen both monitoring and emission reduction measures for PM and NO₂ to alleviate the disease burden of childhood asthma and allergic rhinitis.</p> Graphical Abstract <p></p>