ABSTRACT
The observation that exposure to natural fog has an impact on airway func-
tion was first reported by De Vries et al. in 1964 (1). Subsequently in 1968, two papers published in the United Kingdom (2) and the United States (3)
described the use of ultrasonically nebulized distilled water as an experi-
mental means to induce bronchoconstriction in patients with hyperreactive
airways. Interestingly, Cheney and Butler (3) also observed in their experi-
ments that ‘‘severe coughing occurred in both normal subjects and patients
when distilled water was inhaled from the ultrasonic nebulizer,’’ and that
‘‘inhalation of normal saline from the ultrasonic nebulizer did not produce
coughing in either group.’’ Thereafter, the use of ultrasonically distilled water, also termed ‘‘fog,’’ as a provocative agent in bronchial challenges
spread rapidly. Allegra and Bianco (4) were the first to propose the clinical
use of fog challenge to detect bronchial hyperresponsiveness in asthma and
the method was subsequently standardized by Shoeffel et al. (5). However, it
was principally bronchoconstriction rather than cough that was of interest
to most investigators. Thus, although there is an extensive literature on the
evaluation of the bronchoconstrictor response provoked by inhalation of water solutions, relatively little attention has been devoted to the cough
response evoked by such solutions.
