Even more interesting is that the pattern of switching from breathing out of one nostril to the other happens in a cyclical fashion, with about four hours or so between each switch typically. This can vary from person to person and vary based on your bodily position or nasal congestion.
This “nasal cycle” was first noticed by a German nose specialist, Richard Kayser in 1895. How your nose accomplishes this switch is via erectile tissue in your nose, which is similar to the erectile tissue in a penis or clitoris. Erectile tissue will swell up in one nostril, mostly blocking it, and at the same time erectile tissue in the other nostril will shrink, opening it up for breathing.
Even more interesting is that depending on which nostril you are predominately breathing out of at any given moment, it seems to greatly affect your body and brain.
For instance, a study in 1988 showed that breathing through your right nostril significantly increases blood glucose levels, while breathing through your left nostril has the opposite effect.
It is speculated from this that abnormal nasal cycles, such as breathing through your right nostril for many years without a switch, may be one cause of diabetes.
When you are breathing through your right nostril you will use significantly more oxygen than when breathing through your left.
When you are breathing through your left nostril, the right hemisphere of your brain will be more active or dominant and vice-verse when you are breathing through your right nostril. This can be a handy thing to know as the right hemisphere of your brain is your “creative/ imaginative” side, while the left hemisphere of your brain is your “logical” side. So forcing breathing through one nostril or the other can actually affect the way you think at a given moment.
Even though this switching happens naturally in a cyclical fashion, you can affect it in more ways than just plugging one nostril or the other to force breathing through the one you want. If you lay down on one side or the other, after around 12-15 minutes, the erectile tissue in the nostril on that side will begin to swell up and the other side will decrease its swelling so that if you are lying on your left side, then your right nostril will open up and your left nostril will close up.
It is thought that this nasal cycle could be the reason that, when you sleep on your side, you will often switch sides throughout the night at regular intervals, even if you weren’t in the slightest bit uncomfortable. It could just be that your body needs to switch which nostril it is breathing out of, so you feel the urge to roll over to your other side while you sleep.