Question

Why should we breath only through the nose and not through the mouth?

Answer 1

Answer:

Because the nostrils are smaller than the mouth, air exhaled through the nose creates a back flow of air (and oxygen) into the lungs. And because we exhale more slowly through the nose than we do through the mouth, the lungs have more time to extract from the air we've already taken in.

Explanation:

Answer 2

Breathing through your mouth can cause damage for your teeth and make your through dry. Breathing through your nose is “more healthy” as we could say.