Allergic rhinitis is among the most common chronic allergic diseases and contributes substantially to impaired quality of life and healthcare burden 1. Reliable biomarkers to identify children at risk of developing allergic rhinitis remain limited. Fractional exhaled nitric oxide (FeNO) reflects type 2 airway inflammation and is elevated in children with allergic rhinitis, yet its predictive value for incident allergic rhinitis is largely unexplored, particularly in Asian pediatric populations 2, 3. Using data from the population-based Prediction of Allergies in Taiwanese CHildren (PATCH) schoolchildren cohort, we investigated whether childhood FeNO predicts incident allergic rhinitis in adolescence and young adulthood. We demonstrate that elevated childhood FeNO independently predicts incident allergic rhinitis over 6 years. The PATCH schoolchildren cohort is an ongoing population-based longitudinal study of schoolchildren recruited from a random community sample in northern Taiwan. At baseline (Phase I), 1717 children aged 5–18 years underwent standardized assessments including FeNO, spirometry, and allergen-specific IgE testing 2, 4. Parents completed an ISAAC-based questionnaire. Approximately 6 years later (Phase II), identical procedures were repeated. For the present analysis, we included children with valid baseline FeNO and no physician-diagnosed allergic rhinitis or rhinitis symptoms at baseline. Of 1651 children with valid baseline FeNO, 793 met this eligibility criteria and 577 (72.8%) completed follow-up (Figure S1). Incident allergic rhinitis was defined as new physician-diagnosed allergic rhinitis at follow-up accompanied by rhinitis symptoms in the past 12 months or current medication use. Atopy was defined as a positive allergen-specific IgE result using the Phadiatop Infant result (≥ 0.35 PAU/L). Detailed methods are provided in the Supporting Information. The Institutional Review Board of the Chang Gung Medical Foundation (96-0370B) approved this study. Table 1 shows the baseline characteristics. During follow-up, 69 children (12.0%) developed incident allergic rhinitis. Baseline FeNO levels were higher in those who developed incident allergic rhinitis than in those who did not (24.5 ± 24.8 vs. 16.1 ± 13.2 ppb; p = 0.007), although lower than those observed in children with active allergic rhinitis at baseline (38.3 ± 29.1 ppb; p < 0.001). Atopy and paternal allergic disease were also more common among incident cases. Elevated baseline FeNO independently predicted incident allergic rhinitis (adjusted odds ratio AOR, 5.31; 95% CI, 1.55–18.20) after adjustment for age, sex, body mass index (BMI), preterm birth, atopy, asthma, wheeze ever, parental allergic disease, secondhand smoke exposure, active smoking, FEV1/FVC ratio, and season of sampling (Figure 1A). Predicted probability curves demonstrated a graded increase in risk with increasing FeNO (Figure 1B). Parental allergic disease was also independently associated with incident allergic rhinitis (AOR, 1.79; 95% CI, 1.28–2.50). In contrast, longitudinal change in FeNO was not associated with incident allergic rhinitis (AOR, 1.01; 95% CI, 0.99–1.03). Findings were robust in a sensitivity analysis using a stricter outcome definition requiring both allergic rhinitis and concurrent allergic sensitization at follow-up (Figure S2). Stratified analyses suggested stronger associations in younger children (5–9 years: AOR, 18.01; 95% CI, 3.15–103.05), males (AOR, 8.34; 95% CI, 1.08–64.16), and those with atopy (AOR, 9.59; 95% CI, 2.00–46.04) (Figure 1C). Although interaction tests were not significant, these findings suggest FeNO may be particularly informative for early risk identification in specific subgroups. Future studies with larger sample sizes and more comprehensive modeling of potential interactions among FeNO and other risk factors would be valuable. Our findings extend prior European data showing elevated FeNO levels in adolescents predict incident rhinitis within 4 years 3, and further demonstrate this association in a younger, population-based Asian pediatric cohort over 6 years. FeNO has also been associated with incident asthma 5, 6, supporting shared type 2 inflammatory pathways across upper and lower airway diseases. Several considerations merit discussion. Because asthma and wheeze were uncommon in this analytic sample restricted to children without baseline allergic rhinitis, generalizability to populations with higher asthma prevalence warrants further study. The association between parental allergic disease and incident allergic rhinitis likely reflects shared genetic and environmental influences; however, formal comparison of predictive performance between FeNO and familial history was beyond the scope of this study. FeNO was selected because it is a standardized and widely implemented biomarker of type 2 airway inflammation with established longitudinal data, whereas the predictive value of nasal nitric oxide for incident allergic rhinitis remains uncertain. These novel findings have practical implications. FeNO is a simple, noninvasive measurement that can be implemented into pediatric assessment. Elevated FeNO levels in asymptomatic children may identify those at risk for future allergic rhinitis and possibly asthma, supporting closer monitoring and early preventive strategies. Validation in diverse populations is needed to refine FeNO-based risk stratification. C.-H.W. study design, data analysis and interpretation, and drafting manuscript. J.-L.H. and Y.-L.T. assisted in participant recruitment, cohort maintenance, and acquisition of data. H.-J.T. assisted in data interpretation and critically revising the manuscript. H.-Y.H. assisted in data analysis and data interpretation. T.-C.Y. conception and design, data interpretation, critically revising the manuscript, raising funding acquisition, and supervision. The authors thank the study participants and their parents for their active participation in the PATCH schoolchildren cohort. This work was supported by the National Science and Technology Council, Taiwan (PI: Yao, NSTC 112-2314-B-182-030-MY3, and NSTC 114-2321-B-182-005; PI: Tsai, NSTC 111-2314-B-400-040-MY3; PI: Wang, NSTC 114-2813-C-182-056-B), and Chang Gung Medical Foundation, Taiwan (PI: Yao, CMRP3N0371~3, CMRPG3M1831~3, and OMRPG3Q0031). The authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions. Figure S1: Participant flow diagram. FeNO, fractional exhaled nitric oxide. Figure S2: Association between baseline childhood FeNO levels and incident allergic rhinitis using a stricter outcome definition (sensitivity analysis). Adjusted logistic regression model evaluating the association between baseline FeNO levels and incident allergic rhinitis defined by allergic rhinitis and concurrent allergic sensitization at follow-up. The model was adjusted for age, sex, body mass index, preterm birth, atopy, asthma, wheeze ever, parental allergic disease, secondhand smoke exposure, active-smoking, FEV1/FVC ratio, and season of sampling. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. 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Wang et al. (Mon,) studied this question.