Many people notice one nostril feels clearer than the other. This raises questions about how our noses function: can we truly breathe equally through both, or is this uneven airflow normal? The answer lies in a fascinating, often unnoticed biological process.
The Rhythmic Shift of Nasal Breathing
The sensation of breathing more through one nostril is due to the nasal cycle. This natural, subconscious process involves alternating congestion and decongestion of the nasal passages. Within each nostril are turbinates, shelves of bone covered by soft tissue containing erectile tissue.
During the nasal cycle, turbinates in one nostril swell with blood, causing congestion and restricting airflow. The opposite nostril’s turbinates shrink, increasing airflow. This shift, controlled by the autonomic nervous system, typically alternates every few hours, with a mean duration of about two and a half hours. This alternating function allows one side of the nose to rest, facilitating air humidification, particle filtering, and warming before it reaches the lungs.
Influences on Nasal Airflow
Several common factors can make the nasal cycle more noticeable or temporarily alter airflow. Body position, for instance, influences nasal congestion; lying on one side often causes the lower nostril to become more congested due to gravity. Environmental conditions, such as humidity or temperature changes, can also affect how open nasal passages feel.
Mild allergic reactions or physical exercise can temporarily shift airflow. Allergies cause increased blood flow and swelling in the nasal lining, making congestion more apparent. Conversely, exercise can lead to temporary decongestion due to increased adrenaline. These influences are transient and represent normal variations.
Beyond the Normal Cycle
While uneven nasal breathing often signals the normal nasal cycle, persistent or significant one-sided obstruction can indicate other conditions. Severe allergies or acute infections like colds and sinusitis can cause widespread nasal inflammation and congestion affecting both nostrils, though it may feel worse in one. Nasal polyps, soft, noncancerous growths in the nasal lining, can block passages, leading to persistent stuffiness, reduced smell, or a runny nose.
A common cause of chronic uneven breathing is a deviated septum, where the wall separating the nostrils is off-center. Most people have some septal deviation, but a significant one can obstruct airflow, making one nostril consistently feel more blocked. If nasal breathing difficulties are persistent, severe, or accompanied by symptoms like frequent nosebleeds or chronic sinus infections, seeking medical advice is advisable. For many, however, the sensation of breathing more through one nostril is simply the nasal cycle at work.