Bronchitis can be caused by both viruses and bacteria, although viral bronchitis is much more common.
In most cases, bronchitis is caused by the same viruses that cause the common cold or flu. When someone with a cold or flu virus coughs or sneezes, millions of tiny droplets containing the virus enter the environment via the nose and mouth.
These droplets typically spread up to one meter. After entering the air, they land on surfaces where the virus can survive for up to 24 hours. Anyone who touches these surfaces can spread the virus further by touching something else. Everyday items at home and in public places, such as door handles and keyboards, may have traces of the virus on them.


Most people become infected when they touch a contaminated object, then place their hands near the nose or mouth. It is also possible to breathe in the virus immediately after it enters the environment, before it has had time to settle.

Inhaling Irritants


Bronchitis can also be caused by breathing in irritating substances, including smog, chemicals, or tobacco smoke.


Smoking is the main cause of chronic (long-term) bronchitis. This includes inhaling secondhand smoke, so people who live with smokers may also be at risk.


Occupational Exposure


You may also be at a higher risk of bronchitis and other forms of chronic obstructive pulmonary disease (COPD) if you are regularly exposed to materials that can damage your lungs. These include: grain dust, textiles (fabric fibers), ammonia, strong acids, and chlorine.


This is sometimes referred to as “occupational bronchitis” by physicians. Symptoms usually resolve after you are no longer exposed to the cause of the irritation.

Causes of Acute Bronchitis


Most instances of acute bronchitis are caused by viruses or infections. The same viruses that cause colds and the flu are the most common triggers, but bacterial infections can also cause bronchitis.


Inhaling airborne particles or fumes can irritate your lungs and airways, and will increase your risk for acute bronchitis. This includes inhaling or being exposed to tobacco smoke, dust, exhaust fumes, vapors, or air pollution. If you are exposed to a high level of irritants, such as in an explosion or fire, it may also result in acute bronchitis.
Exposure to can also exacerbate of acute bronchitis.


Causes of Chronic Bronchitis


Chronic bronchitis is caused by repeated irritation and damage of lung and airway tissue. This occurs when a patient regularly breathes in fumes or particles that irritate the lungs. Smoking is the primary cause of chronic bronchitis, but it can also be caused by a variety of other factors. This includes long-term exposure to air pollution, dust and fumes from the environment, and even repeated episodes of acute bronchitis.
People who have chronic bronchitis typically go through periods when symptoms flare up and become much more severe than usual. During these times, they may also develop acute viral or bacterial bronchitis.
The best way to decrease the severity of chronic bronchitis symptoms is to reduce or eliminate exposure to the cause of your chronic bronchitis. Continued exposure to environmental triggers like smoking or air pollution will only make the condition worse over time.