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Throughout the day, our nostrils alternate in inhaling and exhaling without us being aware of it.
This phenomenon is called the ‘nasal cycle’ and plays a significant role in maintaining nasal health.
When we have a cold or allergies, nasal congestion makes breathing difficult.
However, even when there is no such condition, during a deep breath, only one nostril allows air intake at a time.
This is not a cause for concern; what you are experiencing is a natural physiological process.
Scientists say the airflow shifts between nostrils approximately every two hours while we are awake.
However, the rate of this shift decreases during sleep due to reduced air volume inside the body.
The nasal cycle involves two stages: one nostril becoming narrower while the other opens wider.
When the nostril narrows, air flow decreases; when open, it allows a larger volume of air to pass.
The nostril receiving more air becomes tired, as the airflow dries it out, creating conditions for germs to settle. Therefore, nostrils alternate in their breathing function.
This cycle is automatic and regulated by the hypothalamus in the brain.
However, in some individuals, hypothalamic dysfunction means the nasal cycle may not function properly.
Right-handed people often show increased activity in their left nostril.
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Studies indicate that when the right nostril is active, the body is in a stress or alert state.
When the left nostril is active, the body tends to be relaxed.
The nasal cycle is important for several reasons.
Firstly, it protects the upper respiratory system and the nose itself.
Our nose handles about 12,000 liters of air daily, which helps guard against pathogens.
Allowing different nostrils to alternate airflow gives the nose rest and minimizes damage.
If air passed only through one nostril all the time, that passage would dry out, facilitating germ colonization. Thus, the nose needs these periodic breaks in airflow.
When the nose is congested, blood flow inside increases, keeping the surface moist to aid in repair and promoting warm, humid air.
Functions of the Nasal Cycle
The normal functioning of the nose is influenced by many factors.
During a cold, increased mucus production prevents the nostrils from functioning evenly.
Pollen or dust causes significant inflammation of nasal cells, disrupting the nasal cycle.
Certain medications, such as hypertension drugs, can affect the nasal surface because they influence various body cells.
Using nasal decongestants for more than five days can cause rhinitis medicamentosa – a condition resulting in persistent nasal blockage due to medication overuse.
Sudden inflammation inside the nose can also disrupt the nasal cycle.
Structural abnormalities within the nose also impact the nasal cycle.
Nasal polyps affect about 4% of people and interfere with the nasal cycle.
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This causes difficulty in airflow through both nostrils and often leads to congestion.
If any part inside the nose is abnormal, nasal blockage may persist. In such cases, surgery may be necessary to improve breathing and sleep quality.
Problems with airflow through the nose can arise during sleep or when bending over, leading to blood pooling and preventing drainage to the sinuses, which further contributes to congestion and reduced airflow.
The most common cause of nasal blockage is a cold, which typically resolves within two weeks. Sinus congestion may last up to four weeks.
Pollen allergies can also cause persistent nasal symptoms lasting for weeks. Thus, treatment should aim to keep nasal passages open.
If your nasal blockage lasts more than two weeks, it is advisable to consult a doctor. Immediate consultation is especially important if nasal discharge is abnormal in color or consistency.
* Adam Taylor is a Professor of Anatomy at Lancaster University, UK.
* This article was originally published in English by The Conversation and is republished here under a Creative Commons license. To read the original English article, click here.
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