Background: Exposure to ambient particulate matter (PM) has been associated with an increased risk of allergic rhinitis in children. However, it is unclear whether food allergy modifies the association between PM exposure and childhood allergic rhinitis. Objectives: We aimed to evaluate the modification of food allergy on the association between PM exposure and allergic rhinitis in preschool children. Methods: We adopted a cross-sectional study and conducted a questionnaire survey among preschool children aged 3 to 6 years in 7 cities in China from June 2019 to June 2020 to collect information on allergic rhinitis. A mature machine learning-based space-time extremely randomized trees model was applied to estimate early-life, prenatal, and first-year exposure of PM 1, PM 2.5 and PM 10 at 1 × 1-km resolution. We used a combination of multilevel logistic regression and restricted cubic spline functions to quantitatively assess whether food allergy modifies the associations between size-specific PM exposure and the risk of childhood allergic rhinitis. Results: The adjusted ORs for childhood allergic rhinitis among the children with food allergy as per interquartile range (IQR) increase in early-life PM 1, PM 2.5 and PM 10 were significantly higher than the corresponding ORs among the children without food allergy [e.g. OR: 1.57, 95% CI (1.32, 1.87) vs. 1.29, 95% CI (1.18, 1.41), for per IQR increase in PM 1 (9.8 μg/m 3)]. The similar patterns were observed for both prenatal and first-year size-specific PM exposure. The interactions between food allergy and size-specific PM exposure on childhood allergic rhinitis were statistically significant (all p- int < 0.001). Conclusions: Food allergy, as an important part of the allergic disease progression, may modify the association between ambient PM exposure and the risk of childhood allergic rhinitis. Children with food allergy should pay more attention to minimize outdoor air pollutants exposure to prevent the further progression of allergic diseases.

Rhinitis is one of the most prevalent diseases in the world. Indoor microbiome is confirmed to associate with respiratory diseases such as asthma and infections, but no study reported the association between indoor microbiome and the occurrence of rhinitis. In this study, 370 students were randomly selected from 8 junior schools in Terengganu, Malaysia, and self-administered questionnaire and skin prick tests were conducted to define the allergic and non-allergic rhinitis among students. Vacuum dust was collected from the floor and chair/desk surfaces in the classrooms, and culture-independent high-resolution amplicon sequencing and quantitative PCR were conducted to characterize the absolute concentration of bacterial and fungal species. Hierarchical logistic regression was applied in the association analyses. We found similar microbial associations for the students with allergic and non-allergic rhinitis. The microbial richness in Gammaproteobacteria was protectively associated with allergic and non-allergic rhinitis (p = 0.02 and 0.04), and total fungal richness was positively associated with allergic and non-allergic rhinitis (p = 0.01 and 0.03). The absolute concentration of two bacterial species, Aeromonas enteropelogenes and Brasilonema bromeliae, were associated with both types of rhinitis, and six bacterial and one fungal species was associated with either allergic and non-allergic rhinitis (p < 0.005). Four species previously reported as facultative pathogens, including A. enteropelogenes, Escherichia fergusonii, Enterobacter xiangfangensis and Streptococcus salivarius, were protectively (negatively) associated with rhinitis. A higher concentration of two radiation-resistant species, including Deinococcus gobiensis and Deinococcus grandis, were associated with an increased odds of rhinitis.