If a person breathes through their nose then they are more likely to have good breathing. Take a big breath through your mouth and blow it out again. You can take a lot of air in and out of the body this way. Now try doing the same thing only do it through your nose. You can't move any where near the same amount of air through your nose.

When air is inhaled through the nose, it is warmed, moistened and filtered before it reaches the lungs. Air breathed through the mouth does not have a chance to be properly warmed and may cause a shock to the lungs, which respond by tightening the smooth muscle wrapped around the airways in an effort to keep the cold air out.

Mucus lines all the airways, moistening the air as well as trapping dust particles. Small hairs in the nasal passages and larger airways also help to stop dust from getting into the lungs. In the passages from the nose to the back of the mouth are masses of soft tissue filled with lymph nodes, these are called adenoids. There are similar masses at the back of the mouth called tonsils. The purpose of adenoids and tonsils is to trap any infection which enters your body when you breathe. The mucus, hairs, adenoids and tonsils make up a filter system to protect the body from harmful bacteria and particles.

Nasal breathing allows more efficient gas exchange to take place. Try breathing with your nose and then with your mouth. Nasal breathing is similar to breathing through a straw. This increased resistance is essential to set up the correct pressure for efficient gas exchange - it actually increases the uptake of oxygen by 10 to 20 percent.

Recent research suggests that the nose produces a gas called nitric oxide has a role in sterilising the incoming air, preventing mucus from becoming clogged and infected. If we are in the habit of nasal breathing it is less likely to clog.