Upper airway disease and bronchial hyperreactivity.

Bronchial irritability is seen in illnesses involving the upper respiratory tract. In allergic rhinitis, it appears to coexist, and constitutes a risk factor for the development of asthma. In acute respiratory infections, asthmatic attacks may occur coincidentally with viral infections, and infection with some viruses may cause normal persons to develop bronchial irritability. There is suggestive evidence that the associated bronchial irritability may take months to clear and may predispose subjects to permanent hyperreactivity.