Some pranayama breathing practices use alternate breathing techniques where air is exhaled and inhaled though only though right or the left nostril with each inhale or exhale. Alternate breathing practices can be very good for helping to balance out each side of the body.
Some of your more common alternate breathing techniques are usually practiced with pranayama practices such as viloma, anuloma and pratiloma. Some of the more obscure ones date back to early times and are more tied into folk lore and myths and have to do with trying to create magic spells and control the outcome of things by breathing so many times though one side of the sinus on certain times of the moon or day.
Most all people breath different on each side of their bodies, some of it is due to the nasal passages alternating throughout the day and night and different holding patterns on each side of the body. As the average person goes throughout the day one side of the nasal passages is usually different then the other. The right side can be free and open while the leftside is slightly clogged in the morning and by lunchtime it can be the complete opposite and the leftside can be free and open while the right side is slightly clogged and the day after it can be the complete opposite.
Some things like sleeping on one side of your head, squinting from the sun, working hard with one side of the body, etc can lead to that side of the sinuses getting clogged up or swollen. But many people experience differences that don’t follow physical patters that are that obvious. A lot people go throughout the day with the sinus alternating from one side to the next usually every couple of hours or so.
There are a few different theories as to why people sinuses alternate and a lot of the theories go back thousands of years to yogis who studied alternate breathing and the patterns of it. Some think it can be trace to the influences of the sun and the moon or yin and yang and how the influences of each wax and wane throughout the day and night. Some yogis and students have complied charts on these theories it is hard to say if they are accurate until you sit with yourself and find your own subtle breathing patterns and see if they relate or overlap these theories.
Alternate breathing practices can help bring awareness and balance to these uneven breathing patterns. When you separate each side of your breath it can really help to focus on that one side and then compare it to the other side. After a while of this kind of awareness and watching you can start to see your own personal patterns and maybe undo and alter some of them to become more balanced.
Alternate breathing techniques can be a very powerful tool to go along with your yoga and other pranayama practices.