This article is from the Asthma FAQ, by Patricia Wrean and Marie Goldenberg email@example.com with numerous contributions by others.
Bronchitis is an inflammation of the bronchi, the large airways
inside the lungs. (Bronchiolitis is the inflammation of the
bronchioles, the small airways.) This inflammation often leads
to increased mucus production in the airways.
Bronchitis is generally caused either by a virus or by exposure
to irritants such as dust, fumes, or cigarette smoke. If caused
by a virus, the bronchitis will likely be only temporary. In
the case of prolonged exposure to irritants, particularly
cigarette smoking, if there is permanent damage to the bronchi,
bronchitis may become chronic.