Humans have two nostrils, but most tend to focus on using just one side for breathing.
To test this, you can get close to a mirror and exhale through your nose; the mirror will fog up. There will be two spots of condensation on the surface, one for each nostril. However, one spot will be larger than the other because people primarily breathe through one nostril at a time.
Dr. Michael Benninger from the Cleveland Clinic research institute in the United States states that at any given moment, a person breathes approximately 75% through one nostril and 25% through the other. The two nostrils continuously alternate roles throughout the day, a phenomenon known as the nasal cycle.
Right-handed individuals tend to use the left nostril more.
Although we often do not notice this, during the nasal cycle, one nostril may become congested, contributing less air, while the other nostril remains fully open.
According to a 2016 study published in the journal PLOS One, right-handed individuals tend to use the left nostril more.
No one is certain why the nasal cycle exists, but a widely accepted hypothesis suggests that “it relates to allowing moisture to accumulate in one nostril to prevent excessive dryness.”
Dr. Benninger believes that most people are unaware of the nasal cycle. However, it may become more noticeable while sleeping.
For example, if a person lies on their right side, gravity will cause the lower nostril – the right nostril – to become more congested. If the cycle has naturally designated the right nostril to be more congested at that time, it will not have a significant effect. But if the nasal cycle has caused the left nostril to be more blocked and the right nostril to become blocked due to lying on that side, it may lead to difficulty breathing, causing the person to wake up.
Typically, people only notice the cycle if they are consistently congested in one nostril. One way this can occur is if a person has a deviated septum, meaning the wall between the nostrils is displaced, pushing it to one side.
In some people’s noses, soft, painless growths called polyps can also develop, which may cause similar issues. Although less common, tumors can also be related.
While your nose may feel congested when you have a cold, this is not due to the nasal cycle. Essentially, both nostrils are congested when you are sick, so you will have difficulty breathing through your nose regardless of where you are in the cycle.
There are various ways to clear both nostrils at the same time, which can temporarily help us breathe more evenly until the nasal cycle resumes.
Benninger notes that medications such as decongestant sprays, as well as exercising, can have similar effects.
According to a 2021 study published in the Journal of Otolaryngology, sex may also help clear the nasal passages and could be a natural alternative to decongestant medications.
