We recorded lung and forced expiratory volumes, nasal, lower and total airway resistances, closing volume data, the phase III slope and MEFV derivatives on air and helium/oxygen breathing for 24 nonsmoking healthy adults with common colds who were then randomly assigned to inhalation of a mixture of aromatic vapors (eucalyptus, menthol, camphor) or a tap water control. Measurements were made after 20 and 60 min of aromatics or control exposure and after intranasal spraying with a 0.25% phenylephrine solution. Gas chromatography of sampling tubes gave the aromatics concentration in the inspired air.Although baseline differences from predicted values were limited to changes in small airways function, except for the reduced peak expiratory flow rate (PEFR) mean, low-density gas breathing responsivity suggested concomitant large airway involvement. Significant changes (p = 0.05) in forced vital capacity, forced expiratory volume for the 3rd s, closing capacity and the phase III slope of the alveolar plateau favored aromatics therapy over the control solution, with marginal volume of isoflow differences showing a similar trend. Intranasal phenylephrine induced statistically significant changes in nasal resistance and in tests of the large and small airways.In confirming the presence of peripheral airways dysfunction in nonsmokers with uncomplicated common colds, our data imply that the changes can be modified favorably by short-term aromatics inhalation. The prompt responses to intranasal phenylephrine suggest that the operation of a nasal-pulmonary reflex arc may be responsible, in part, for the lower airways effects of the aromatics vapor.