Causes of bronchitis 

The bronchitis infection can be caused by either a virus or 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. The virus is contained in the millions of tiny droplets that come out of the nose and mouth when someone coughs or sneezes.

These droplets typically spread about 1m (3ft). They hang suspended in the air for a while, then 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. People usually become infected by picking up the virus on their hands from contaminated objects, and then placing their hands near their nose or mouth. It is also possible to breathe in the virus if it is suspended in airborne droplets.

Read more about how cold and flu germs spread.

Breathing in?irritant substances

Bronchitis can also be triggered by breathing in irritant substances, such as smog, chemicals in household products or tobacco smoke.

Smoking is the main cause of long-term (chronic) bronchitis, and it can affect people who inhale second-hand smoke, as well as smokers themselves.

Read information about treatments to quit smoking.

Occupational exposure

You may also be at risk of bronchitis and other forms of?chronic obstructive pulmonary disease (COPD) if you are often exposed to materials that can damage your lungs, such as:

  • grain dust
  • textiles (fabric fibres)
  • ammonia
  • strong acids
  • chlorine

This is sometimes referred to as "occupational bronchitis", and usually eases once you are no longer exposed to the irritant substance.

Read more information about the causes of COPD.

You can also read?the?Health and Safety Executive's 2013?report on COPD in Great Britain?attributed to occupational exposure (PDF, 58kb).

Media last reviewed: 07/01/2013

Next review due: 07/01/2015


Page last reviewed: 14/07/2014

Next review due: 14/07/2016