You might sometimes notice that one nostril feels more open than the other. This common sensation signals a completely normal physiological process within your body. This alternating airflow is a regular part of how your nose functions to maintain its health and efficiency.
The Nasal Cycle: A Natural Phenomenon
The feeling of one nostril being more open than the other is due to the nasal cycle. This continuous, unconscious process involves the two sides of your nose alternating their primary role in airflow. While one nostril becomes more congested, the other simultaneously decongests, creating a noticeable difference in air passage. The nasal cycle ensures airflow periodically shifts between nostrils, maintaining relatively constant total resistance. This alternating pattern typically lasts about two and a half hours, though duration varies.
The Science Behind the Switch
This alternating congestion and decongestion involves the autonomic nervous system, which controls involuntary bodily functions. Its sympathetic and parasympathetic branches regulate blood flow to specialized erectile tissue in the nasal passages, known as the turbinates. When the sympathetic nervous system is more active in one nostril, blood vessels in the turbinates constrict, leading to decongestion and increased airflow. Conversely, increased parasympathetic activity in the other nostril causes vasodilation, where blood vessels expand and fill with blood. This makes the turbinates swell and the nasal passage become more congested, creating the sensation of one nostril being more open and the other more closed.
Why Your Nose Cycles
The nasal cycle serves several functional purposes for respiratory health. This alternating airflow prevents the delicate nasal lining and cilia—tiny hair-like structures that filter inhaled air—from drying out. Allowing one nostril to rest and recover helps its mucous membrane rehydrate and maintain effectiveness in trapping particles and humidifying air. Differing airflow rates in each nostril also optimize the sense of smell, or olfaction. Some scent molecules are better detected with faster airflow, while others are more easily perceived with slower, prolonged exposure to olfactory receptors.
Factors Affecting Nasal Airflow
Several everyday factors can influence the nasal cycle and make airflow differences more noticeable. Body position plays a role; for example, lying on one side can increase congestion in the lower nostril due to gravity. Changes in ambient temperature can also affect nasal blood flow and alter the perception of nasal patency. Physical activity, such as exercise, often causes temporary decongestion of both nostrils, leading to clearer breathing. Minor environmental irritants can also temporarily influence the degree of congestion in either nostril.