What is "nasal cycle"

n. The periodic alternation in the use of the left or the right nostril more actively for breathing, occurring in humans, caused by periodic swelling of the nasal conchae on one side of the nose and its reversal.

The nasal cycle is the often unnoticed alternating partial congestion and decongestion of the nasal cavities in humans and other animals. It is a physiological congestion of the nasal concha, also called the nasal turbinate, due to selective activation of one half of the autonomic nervous system by the hypothalamus. It should not be confused with pathological nasal congestion. Although various aspects of the nasal cycle have been studied and discussed in the ancient Yogic literature, in the modern western literature, it was first described by the German physician Richard Kayser in 1895.