Wheezing is a whistling noise of varying pitch and loudness that
occurs when the small airways become narrower because of inflammation or a
buildup of mucus and dead cells in the airway. As these small air passages
become narrower, wheezing may be heard when the person breathes out. As the
passages continue to narrow, wheezing may be heard when the person breathes
both in and out.
When a person has severe difficulty breathing, wheezing may no
longer be heard because very little air is moving through the narrowed
airways.
A doctor may order a chest X-ray or breathing test (spirometry) to
determine the cause of a person's wheezing. Some causes of wheezing include
bronchitis, allergies, or asthma. Treatment depends on the cause of the
wheezing and may include medicines, an inhaler, or a machine to help a person
breathe.