The nasal cycle is the unconscious alternating partial congestion and decongestion of the

nasal cavities The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nasal c ...

in humans and other animals. This results in greater airflow through one nostril with periodic alternation between the nostrils. It is a physiological congestion of the

nasal concha In anatomy, a nasal concha (), plural conchae (), also called a nasal turbinate or turbinal, is a long, narrow, curled shelf of bone that protrudes into the breathing passage of the nose in humans and various animals. The conchae are shaped like ...

e, also called the nasal turbinates (curled bony projections within the nasal cavities), due to selective activation of one half of the autonomic nervous system by the

hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamu ...

. It should not be confused with pathological

nasal congestion Nasal congestion is the blockage of nasal breathing usually due to membranes lining the nose becoming swollen from inflamed blood vessels. Background In about 85% of cases, nasal congestion leads to mouth breathing rather than nasal breathing. ...

Description

The nasal cycle was studied and discussed in the ancient Indian

yoga Yoga (; sa, योग, lit=yoke' or 'union ) is a group of physical, mental, and spiritual practices or disciplines which originated in ancient India and aim to control (yoke) and still the mind, recognizing a detached witness-consciou ...

of literature of

pranayama Pranayama is the yogic practice of focusing on breath. In Sanskrit, '' prana'' means "vital life force", and ''yama'' means to gain control. In yoga, breath is associated with ''prana'', thus, pranayama is a means to elevate the '' prana'' ''sha ...

. In the modern western literature, it was first described by the German physician Richard Kayser in 1895. In 1927, Heetderks described the alternating

turgescence Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels tight, the area ma ...

of the inferior

turbinates In anatomy, a nasal concha (), plural conchae (), also called a nasal turbinate or turbinal, is a long, narrow, curled shelf of bone tissue, bone that protrudes into the breathing passage of the nose in humans and various animals. The conchae ar ...

in 80% of a normal population. According to Heetderks, the cycle is the result of alternating congestion and decongestion of the nasal conchae or turbinates, predominantly the inferior turbinates, which are by far the largest of the turbinates in each nasal fossa. Turbinates consist of bony projections covered by

erectile tissue Erectile tissue is tissue in the body with numerous vascular spaces, or cavernous tissue, that may become engorged with blood. However, tissue that is devoid of or otherwise lacking erectile tissue (such as the labia minora, the vestibule/vagina an ...

, much like the tissues of the penis and clitoris. The turbinates in one fossa fill up with blood while the opposite turbinates decongest by shunting blood away. This cycle, which is controlled by the

autonomic nervous system The autonomic nervous system (ANS), formerly referred to as the vegetative nervous system, is a division of the peripheral nervous system that supplies viscera, internal organs, smooth muscle and glands. The autonomic nervous system is a control ...

, has a mean duration of two and a half hours but varies widely with age, body-posture, and other conditions. He further observed and documented that the turbinates in the dependent

nasal fossa The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nasal c ...

fill when the patient is in the lateral decubitus position. The nasal cycle is an alternation in both time and between left and right sides, with the total resistance in the nose remaining constant. The asymmetric airflow may have some benefit to overall olfactory sensitivity. In patients with a fixed septal deviation and intermittent nasal obstruction, the interplay of the nasal cycle becomes evident; the sensation of obstruction frequently mirrors the congestion phase. It is possible that the nasal cycle may exacerbate the

caused by the common cold, as the lack of motility of the cilia in one half of the nose may lead to an uncomfortable sensation of not being able to shift mucus by

blowing the nose Nose-blowing is the act of expelling nasal mucus by exhaling forcefully through the nose. This is usually done into a facial tissue or handkerchief, facial tissues being more hygienic as they are disposed of after each use while handkerchiefs are ...

Benefits for breathing

It has been shown that the cilia of the congested side suspend their motility until that side decongests. Thus the cycle ensures that one side of the nose is always moist, to facilitate humidification, which is one of the three functions of the nose, the other two being filtration and warming of inspired air prior to its entering the lungs.

Benefits for olfaction

Some odor chemicals bind with olfactory receptors easily, even under conditions of high airflow, and other odors need more time, under low airflow conditions, to bind with receptors. With high airflow on one side and low airflow on the other side, the olfactory center detects a greater range of smells.

Distinction

The nasal cycle should not be confused with

pathological Pathology is the study of the causal, causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when us ...

nasal congestion: individuals with normal nasal breathing usually do not realize their breathing is asymmetric unless there is underlying nasal obstruction. In pathological conditions, however, the nasal cycle may influence the symptoms.

Research on the effects

In 1994, breathing through alternate nostrils showed effects on

brain hemisphere The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres ...

symmetry on

EEG Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex ...

topography. D.S. Shannahoff-Khalsa published in 2007 on the effect of this cycle and manipulation through forced nostril breathing on one side on the endogenous

ultradian In chronobiology, an ultradian rhythm is a recurrent period or cycle repeated throughout a 24-hour day. In contrast, circadian rhythms complete one cycle daily, while infradian rhythms such as the human menstrual cycle have periods longer than ...

rhythms of the autonomic and central

nervous system In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes th ...

. More recent research has shown no statistically significant correlation between spontaneously (i.e. not forced) dominant nostril and active brain hemisphere.

References

{{Authority control Nose Autonomic nervous system