Natural pollen exposure increases in a dose-dependent way Fraction of exhaled Nitric Oxide (FeNO) levels in patients sensitized to one or more pollen species.

Airways inflammation, evaluated by FeNO, increases in dose-dependent manner from subjects monosensitized to pollen species to those poly-sensitized, especially when asthma-like symptoms on pollen exposure are also reported. This should be considered by allergists during natural pollen seasons when evaluating both pulmonary function and airways inflammation.