Why One Nostril Always Feels More Open Than the Other: The Nasal Cycle Explained

Have you ever noticed that for part of the day, one nostril feels more “open” while the other is more congested and later, they swap? That phenomenon is the nasal cycle, a built-in process in nearly all healthy adults. It is the spontaneous congestion and decongestion of the nasal mucosa where one side of the nose becomes temporarily more restricted while the other side is freer. ¹

What Is the Nasal Cycle?

The nasal cycle is a normal physiological rhythm driven by changes in blood volume within the nasal mucosa, especially in the turbinates and nasal septum.

As one side’s blood vessels engorge, that side becomes more congested; at the same time, the opposite side decongests. Over time, they alternate.² In about 70–80% of adults, this cycle is present.²

Pendolino and colleagues categorize nasal cycle patterns into four types:

• Classic: reciprocal congestion/decongestion with constant total volume

• Parallel: both sides congest or decongest simultaneously

• Irregular: alternating but without a definite pattern

• Acyclic: no clear cyclic change or difference in nostril volumes.²

In a study of healthy volunteers, Pendolino et al. found that 19 of 30 participants displayed a “parallel” pattern, and 11 showed the “classic” pattern. Interestingly, the differences in subjective nasal obstruction did not differ significantly between those groups.³ This suggests that even when the mucosal changes occur, individuals may not feel marked differences.

Why Does the Nasal Cycle Occur?

Researchers believe that the nasal cycle provides several physiological functions:

• Air conditioning: alternating airflow may help with humidifying, warming, and filtering inhaled air.

• Mucosal rest: by shifting which side receives more airflow, mucosal tissues may recover from constant exposure.

• Defense mechanism: changes may assist in immune defense by varying exposure to inhaled particles.²

The regulation is thought to involve the autonomic nervous system (sympathetic and parasympathetic control) influencing blood flow to nasal tissues.⁴ In a popular Instagram reel by, Dr. Amir Khan, NHS general practitioner and a health practitioner recently explained this phenomenon in Lorraine.

When the Cycle Becomes Noticeable or Problematic

For most people, the nasal cycle is subtle and unnoticed. However, it becomes noticeable when one side’s congestion is exaggerated by a condition such as allergic rhinitis, a deviated septum, or upper respiratory infection. That is when a person may feel like they “can’t breathe through one nostril” persistently.⁵

In such cases, a clinician must differentiate between normal cycle and pathologic nasal obstruction. Nasal cycle awareness is important during evaluation, especially before interventions like septal surgery or turbinate reduction because an instantaneous airflow measurement may not reflect the patient’s overall nasal function across the day.²

Clinical Implications & Evaluation

When assessing nasal airflow, ENT specialists use tools like peak nasal inspiratory flow (PNIF), rhinomanometry, or imaging (MRI/CT) to document mucosal changes over time.² Longitudinal measurements help distinguish normal cyclic changes from structural blockages.

Moreover, a 2019 study looking at the relationship between nasal cycle, symptoms, and nasal cytology (cells lining the mucosa) found that nasal cycle pattern had no significant correlation with subjective obstruction scores or nasal cytology (inflammatory findings) in healthy volunteers.³ This indicates that typical nasal cycles may not directly cause symptoms in most individuals.

Conclusion

The nasal cycle is a fascinating, automatic process built into our respiratory system. It demonstrates how our body fine-tunes nasal airflow throughout the day. While it rarely causes symptoms, awareness of this cycle helps ENT doctors and patients avoid misdiagnosing normal variation as disease. In evaluating nasal obstruction, clinicians must consider both structural and cyclical factors to guide appropriate treatment.

References:

1. Pendolino, Alfonso Luca et al. “Relationship Between Nasal Cycle, Nasal Symptoms and Nasal Cytology.” American Journal of Rhinology & Allergy (2019). PMC7207008.

2. Pendolino, A. L., Lund, V. J., Nardello, E., Ottaviano, G. The Nasal Cycle: A Comprehensive Review. Rhinology Online, Vol. 1, 2018.

3. Pendolino, A. L., et al. “Relationship Between Nasal Cycle, Nasal Symptoms and Nasal Cytology.” (analysis of healthy volunteers) PMC7207008.

4. Eccles, R. “Sympathetic Control of Nasal Erectile Tissue.” European Journal of Respiratory Diseases Supplement (1983).

(Rh/Eth/TL/MSM)