Cover each nostril in turn and breathe in through your nose. One nostril will be easier to breathe in through. Now try it again a few times over a day. I belie

Cover each nostril in turn and breathe in through your nose. One nostril will be easier to breathe in through. Now try it again a few times over a day. I believe the reason your body does this is to allow your olfactory system to pick up a greater range of smells: Some chemicals are easier to pick up when the air is traveling slower.