Alternate nostril breathing and the nasal cycle

Your nose takes turns by itself

The German physician Richard Kayser described it in 1895. Inside the nose there's erectile tissue, mostly at the front of the septum and in the lower turbinate. When it fills with blood on one side, that side narrows and the other opens up. After a while, they trade places.

The switch is run by the autonomic nervous system, the same one that manages your pulse and digestion without your input. Because the nose's total resistance stays about the same, hardly anyone notices, unless there's an underlying blockage.

How long a turn lasts

A 2016 study by Kahana-Zweig and colleagues tracked airflow in each nostril in 33 healthy adults with a wearable device, for up to 26 hours at a stretch. The average cycle ran 2.15 hours, with huge variation: from 15 minutes to more than 10 hours, depending on the person.

The cycle shifted with the body's state. Awake, people switched about every two hours on average; asleep, about every four and a half, with a sharper difference between the two sides. The authors tie it to the body's overall level of arousal. Posture matters too: it's been known since 1927 that when you lie on your side, the lower nostril tends to congest.

What it might be for

There's no settled answer. One proposal is that the switch lets half the nose rest and stay moist while the other half works. Another has to do with smell: some odors register better in fast-moving air and others in slow, so two nostrils running at different speeds would cover more of them. These are reasonable hypotheses, not established facts.

What yoga did with it

The Hatha Yoga Pradipika, a 15th-century manual, teaches drawing air in through the left nostril and letting it out through the right, then the reverse. It calls the right nostril the solar one and says the practice leaves the nadis clean. Nadis are the channels that carry vital energy in yoga's view of the body. That's a tradition's map, not an anatomical description.

Three breathings on this site come from there. Alternate nostril breathing (nadi shodhana) goes back and forth between the two sides. Moon breath (chandra bhedana) always goes in through the left and out through the right. Sun breath (surya bhedana) does the opposite. The tradition assigns different effects to each side. Science hasn't clearly confirmed that difference.

Does each nostril switch on one side of the brain?

It's the most repeated idea, and the evidence doesn't hold it up well. A 1994 study suggested that deliberately alternating nostrils changed the symmetry of the brain's electrical activity. But in 2008, Samantaray and Telles tested the popular version on 289 people: they compared those whose right nostril was dominant with those whose left was, on a verbal task tied to the left hemisphere. They found no significant difference.

The 2016 study sums up where things stand. Some work finds more brain activity on the same side as the open nostril, some on the opposite side. Nobody knows, either, whether the brain drives the nose or the nose influences the brain. Its authors say the question remains unresolved.

What studies say about the practice

A 2017 systematic review by Shreya Ghiya gathered 44 randomized trials of alternate nostril breathing. It concluded that the practice affects the autonomic nervous system and heart and lung function, and that regular practice was linked to better scores on cognitive tests.

Read it with its limits, which the author lists herself. Ten of the trials carried a high risk of bias. Most enrolled healthy people. Each trial used a different variation, there's no standard method, and how much or how often to practice is still unknown. On top of that, alternate nostril breathing is also slow, attentive breathing, and it's hard to tell which part does what. The evidence is large in number and modest in quality.

How to try it

Alternate nostril breathing (nadi shodhana) on this site uses 4 seconds a phase: in through the left, out through the right, in through the right, out through the left, for 5 minutes. You'll notice one side pushes back more. That's the nasal cycle, and there's nothing to overcome: just let less air through on that side.

Alternate nostril breathing with holds adds 4 seconds with the air in and an 8-second exhale. Save it for when the first one feels comfortable. If your nose is stuffed up from a cold or allergies, wait for another day. If you feel dizzy or short of breath, lower your hand and breathe normally. And if you're pregnant or have a heart, lung or blood pressure condition, check with your care provider first.