The Nasal Cycle: Why Your Body Uses One Nostril at a Time to Breathe
At least 12,000 litres of air pass through the nose each day, making it a crucial front-line defence against pathogens. This immense volume highlights the nose's vital role in filtering and conditioning the air we breathe, but it also underscores why a unique bodily process, known as the nasal cycle, is essential for maintaining respiratory health.
Understanding the Nasal Cycle
Even when you are not sick, you might notice that taking a deep breath often involves only one nostril allowing air in. This is not a sign of illness but a normal, automatic process regulated subconsciously by the hypothalamus in the brain. The nasal cycle involves nostrils alternating between dominance for airflow, switching as frequently as every two hours while awake, though less often during sleep when breathing slows.
During the congestion phase, one nostril experiences reduced airflow, while the opposite nostril is open or decongested, facilitating more air passage. This decongested phase can fatigue the open nostril as air dries it out and exposes it to pathogens, necessitating the swap to protect nasal tissues.
Key Functions and Benefits
The nasal cycle serves multiple important purposes. First, it protects the lining of the nose and respiratory system by reducing the risk of damage from constant air exposure. Alternating dominance allows each nostril time to rest and repair, preventing dryness and inflammation that could make it easier for pathogens to cause harm.
Additionally, increased blood flow during congestion helps moisten the nostrils, ensuring air is warmed and humidified as it passes through. Studies suggest that the dominant nostril may influence bodily states, with the right nostril linked to alertness or stress and the left to relaxation, though this varies among individuals.
Factors Affecting the Nasal Cycle
Several factors can disrupt the nasal cycle's normal function. Respiratory conditions like colds and flu increase mucous production, restricting nasal passage alternation. Allergens such as pollen or dust mites cause severe inflammation, impeding proper cycle operation.
Medications for high blood pressure can irritate the nasal lining by affecting blood vessels, including those in the nose. Overuse of nasal decongestants for more than five days can lead to rhinitis medicamentosa, a form of congestion that swells nostril tissues and disrupts the cycle.
Structural issues also play a role. Nasal polyps, found in up to 4% of people, are outgrowths that limit airflow, making the cycle ineffective and causing constant blockage. A deviated nasal septum, where the cartilage between nostrils is off-centre, often requires surgery to improve breathing and sleep quality.
Even simple factors like lying down or slouching can affect the cycle. Gravity causes blood to pool in nasal tissues and sinus contents to move into the nostril closest to the pillow, potentially blocking one side and hindering normal function.
When to Seek Help
If you experience blocked nostrils, common culprits include infections like colds and flu, which can take up to two weeks to clear, or sinusitis lasting four weeks. Pollen allergies may also disrupt the nasal cycle for weeks, with antihistamines offering relief during hay fever season.
Persistent blockage in one nostril for over two weeks, especially with abnormal mucus or discharge, warrants medical attention to rule out underlying issues. Understanding the nasal cycle not only demystifies everyday breathing but emphasises the importance of nasal health in overall well-being.
