What causes bronchitis to occur according to common medical understanding?

Bronchitis is primarily caused by long-term exposure to irritants, with smoking being the most significant factor. When an individual is exposed to cigarette smoke or other environmental pollutants over an extended period, the airways become inflamed and can produce excess mucus. This chronic irritation leads to the typical symptoms associated with bronchitis, including coughing, wheezing, and difficulty breathing.

While bronchitis can also result from viral or bacterial infections, those are more often causes of acute bronchitis rather than chronic bronchitis, which is the focus of this question. Short-term exposure to allergens can lead to respiratory issues as well, but they do not typically result in bronchitis, which is characterized by long-lasting inflammation of the bronchial tubes. Understanding these details is key in recognizing how different factors contribute to the condition.