OBJECTIVE: Few studies have investigated links between fraction exhaled nitric oxide (FeNO), the home and the school environment. FeNO is a biomarker of T helper 2 (Th2) airway inflammation. We investigated associations between FeNO and airway symptoms, allergies, household and classroom exposure among pupils in ten primary schools in Stockholm (N = 415). METHODS: Information on health and household environment was obtained by a questionnaire. FeNO was measured at school. Particle mass (PM RESULTS: In total, 9.7 % of the pupils had elevated FeNO (>
20 ppb), 15.2 % doctor diagnosed asthma, 10.7 % current asthma, 17.8 % reported allergy and 9.6 % doctor diagnosed allergy. Reported allergy (p = 0.02), diagnosed allergy (p = 0.002), and current asthma (p = 0.007) were associated with elevated FeNO. Children living in single-family houses with basement had higher FeNO than those in self-owned apartments (p = 0.001). In the classrooms, PM CONCLUSIONS: FeNO is associated with reported asthma and allergy. In the school environment, PM