Background: A positive relation between exhaled nitric oxide (NO) levels and allergen exposure has been found in some studies whereas there is less information on how non-allergen environmental factors influences exhaled NO.
Objective: To study the relationship between exhaled NO levels in schoolchildren in relation to IgE sensitisation and allergenic and non-allergenic environmental factors.
Method: This study comprised 374 schoolchildren (13-14 years of age) who performed exhaled NO-measurements and skin prick tests. Exposure to allergens, respiratory infections, environmental tobacco smoke and home window pane condensation, the latter an indicator of high humidity and poor ventilation was evaluated through questionnaires.
Results: In IgE-sensitised children sensitisation to pets was a more important determinant of exhaled NO than sensitisation to pollen. Higher NO levels were found in cat-sensitised children with a cat or other furred pets at home compared to cat-sensitised children without pets (geometric mean, 24.0 vs. 13.9 ppb, P=0.03). Significantly higher exhaled NO levels were found in non-sensitised children that reported having a cold (5.7 vs. 3.8 ppb, P<0.001) or lived in homes with window pane condensation (7.1 vs. 4.4 ppb, P=0.01) than in non-sensitised children without a cold and window pane condensation, respectively. These associations were not found in children that were sensitised to inhalation allergens.
Conclusion: Allergen exposure seems to be the most important determinant for exhaled NO levels in IgE-sensitised children whereas in non-sensitised children NO levels were associated with respiratory infections and home window pane condensation.