The sensation of one nostril feeling persistently blocked is common. Nasal congestion occurs when the delicate tissues lining the nose swell, narrowing the airway and restricting airflow. While temporary congestion often points to a cold or allergies, an ongoing, one-sided blockage can be caused by normal physiological processes or underlying anatomical issues. Understanding the difference between normal nasal function and a true obstruction clarifies why this asymmetrical blockage occurs.
The Nasal Cycle
The most frequent reason for alternating nostril blockage is the nasal cycle, a completely normal, built-in process. This process involves the autonomic nervous system, which regulates blood flow to the turbinates. Turbinates are structures inside the nose that humidify, filter, and warm the air we breathe.
The nasal cycle causes the turbinates in one nostril to swell with blood, leading to congestion and reduced airflow. Simultaneously, the opposite nostril decongests, opening that passage for easier breathing. This natural alternation allows the congested side’s mucous membranes to rest and recover, preventing them from drying out. The cycle typically shifts every two to six hours.
Structural Causes of Persistent Blockage
While the nasal cycle explains temporary asymmetry, a constant, one-sided blockage often suggests a fixed anatomical problem. The most common structural issue is a deviated septum, where the thin wall separating the nasal passages is off-center. This displacement permanently narrows the airflow channel on the side of the deviation.
Another frequent cause is turbinate hypertrophy, the chronic enlargement of the turbinates themselves. If one nostril is narrower due to a deviated septum, the turbinate on the opposite side may enlarge in a compensatory effort to regulate total airflow. This hypertrophy involves a lasting change in tissue size that significantly restricts breathing.
Inflammatory and Immune System Triggers
Chronic congestion can stem from persistent swelling caused by inflammatory responses. Chronic allergic rhinitis, or hay fever, involves an ongoing immune reaction to airborne substances like pollen or dust mites. This persistent exposure triggers inflammatory chemicals, leading to mucosal swelling that can affect one passage more severely.
Other Inflammatory Causes
Non-allergic rhinitis also causes chronic inflammation, triggered by environmental irritants such as smoke, strong odors, or temperature changes. Additionally, nasal polyps, which are soft, non-cancerous growths, can physically block one side of the nasal passage. These growths arise from chronic inflammation and can lead to persistent stuffiness and a reduced sense of smell.
When to Seek Professional Diagnosis
If a unilateral nasal blockage lasts longer than a few weeks or severely impacts sleep, seek a medical evaluation. Persistent congestion warrants professional attention to determine the underlying cause. Red flags suggesting a more serious condition include recurrent nosebleeds, facial pain or swelling, or a profound loss of smell.
A specialist, such as an otolaryngologist, can use nasal endoscopy to inspect the internal structures. Identifying whether the issue is a fixed anatomical problem or a chronic inflammatory condition guides the treatment plan. Treatment may involve medication, like steroid nasal sprays for inflammation, or surgical correction for structural issues.