If you have ever noticed that one nostril is more congested than the other without having a cold, you are not facing an anomaly, but a natural physiological process known as the nasal cycle. First described by German physician Richard Kayser in 1895, this autonomic phenomenon causes 70 % to 80 % of people to breathe predominantly through a single nostril most of the time, alternating sides every two to six hours.
This constant relay is orchestrated by the autonomic nervous system. Through sympathetic and parasympathetic signals, the body dilates the erectile tissues of the turbinates in one nostril, swelling their blood vessels and partially blocking airflow. At the same time, in the opposite nostril, the vessels constrict, opening the airway to maximum flow. Hours later, the pattern reverses completely and imperceptibly.
This dynamism fulfills two biological functions crucial for well-being:
- Epithelial protection: Constant airflow dehydrates mucous membranes. The nostril 'on pause' takes advantage of the reduced flow to regain moisture, restore the movement of its cilia, and clear trapped pathogens.
- Olfactory calibration: A Stanford University study published in Nature showed that odorant substances are absorbed at different rates. Fast-absorbing molecules are better captured in the fast-flowing nostril, while slow-absorbing ones require the slow flow of the semi-congested nostril to be detected.
Thanks to this ingenious mechanism, the human body optimizes its olfactory spectrum and safeguards the first defensive barrier of its lungs without interruption.
Source: Nature (Sobel et al., 1999: 'The world smells different to each nostril') / The Laryngoscope
