Question

why it is not advisable to breathe through mouth?

Answer 1

that is because mouth caanot filter the air in which dust particle present but the nose can filter the air so we breath clear air.

hope it will help y

Answer 2

Taking breathe though nose gives you more purified air as compared to mouth.
As hair in your nose stops the particles to enter as much as possible.
So Breathe though nose.
Hope you got your answer.