Factors affecting measured FeNO levels1
| Factors which increase FeNO | Factors that decrease FeNO |
| Allergic rhinitis in patients exposed to an allergen and atopic dermatitis | Cigarette smoking (acutely and cumulatively) |
| Increased height | Childhood (<12 years old). This is less important in adolescence and not significant in adulthood |
| Rhinovirus infection in healthy individuals |
FeNO, fractional exhaled nitric oxide.