Why one nostril always feels blocked - and what it may do to your brain

If you've ever felt that only one nostril is truly "open," you're not imagining it. It's a well-known natural phenomenon called the nasal cycle, in which airflow is greater through one nostril before gradually shifting to the other. The nasal cycle has been documented in previous research. More recently, scientists have also examined what happens when people intentionally breathe through only one nostril and whether that affects brain activity, mood and mind wandering. Throughout the day, the nostrils alternate in dominance, with one carrying more airflow than the other. This shift can occur about every two hours while a person is awake and less frequently during sleep. The process involves alternating congestion and decongestion of the nasal tissues and is thought to allow the nasal lining to rest, stay moist and help protect against pathogens, according to CNN. The cycle occurs automatically and is controlled by the hypothalamus, which regulates many physiological processes throughout the body. What happens in our noses during the day? A 2016 study published in PLOS One monitored the nasal cycle for 24 hours in 33 healthy participants. Every participant showed regular alternation between the right and left nostrils. The average cycle lasted about 2.02 hours while participants were awake and about 4.5 hours during sleep, meaning the cycle slowed at night. Researchers also found that the nasal cycle was more pronounced during sleep, with a greater difference in airflow between the nostrils, while airflow was more balanced during waking hours. The study also found that all participants, who were right-handed, spent slightly but significantly more time with the left nostril dominant. On average, left-nostril dominance lasted 2.63 hours compared with 2.17 hours for the right nostril. In addition, slower breathing was associated with a stronger dominance of one nostril. Researchers also documented a relationship between body position and airflow: lying on one side was associated with greater airflow through the opposite nostril. "The nasal cycle is a natural physiological process that occurs autonomously around the clock," explained Dr. Avital Fellner, an ear, nose and throat specialist and head of otolaryngology for Clalit's Dan-Petah Tikva district. "During this cycle, every few hours the lining of one nostril becomes more congested while congestion decreases in the other. Despite these changes, the overall resistance to airflow through the nose remains nearly constant, so under normal circumstances most people aren't even aware that the process is taking place." People with normal nasal breathing may occasionally notice the cycle when breathing slowly through their noses, she said. "It's important to emphasize that this is an automatic process that cannot be consciously controlled," Fellner said. "The only factor that can influence it to some extent is a change in body position, such as lying on your side. When you lie on your right side, airflow through the left nostril improves, and vice versa. Even then, the effect is limited, and there is no conscious or medication-based way to alter the cycle itself. For that reason, breathing exercises are not effective for changing the nasal cycle." The nose's built-in defense mechanism Experts say the nasal cycle also serves an important function. At least 12,000 liters of air pass through the nose each day, so alternating airflow between the nostrils may reduce strain, prevent the nasal lining from drying out and help the respiratory system cope with pollutants and pathogens. Colds, influenza, allergies, overuse of decongestant nasal sprays, nasal polyps and a deviated septum can disrupt the cycle and lead to a prolonged feeling of nasal blockage. During a cold, congestion may last up to two weeks, while sinusitis can persist for as long as four weeks. If one nostril remains blocked for more than two weeks, especially if accompanied by unusual discharge, experts recommend seeing an ear, nose and throat specialist. Some studies have suggested that when the right nostril is dominant, the body tends to be in a more alert or stressed state, while left-nostril dominance is associated with a calmer state. What happens when you deliberately breathe through one nostril? In recent years, research has shifted from asking why the dominant nostril changes to whether breathing through the right versus the left nostril has different effects. A 2024 pilot study published in Brain Sciences followed 20 adults over eight days of practicing one-nostril breathing. Ten participants breathed only through the left nostril, while the other 10 breathed only through the right. Before and after each session, participants rated stress, restlessness, calmness, happiness and mental clarity. Researchers also measured mind wandering after each session. Both groups reported overall improvements in well-being. Stress and restlessness declined significantly, calmness increased significantly and happiness rose modestly. Mental clarity, however, did not change significantly. Participants also experienced less mind wandering over the eight-day period. The researchers found differences between the two breathing methods. Right-nostril breathing was more strongly associated with reduced stress and restlessness and greater calmness. Left-nostril breathing appeared to be more effective at reducing mind wandering over time. The authors concluded that both techniques may improve psychological well-being, though in different ways. Right-nostril breathing appeared to have a stronger effect on mood and stress, while left-nostril breathing had a greater impact on mind wandering. The researchers cautioned, however, that the study was small. It included only 20 participants, had no control group and relied on self-reported measures. A deviated septum Fellner noted that a substantial portion of the population has a deviated septum, a condition in which the wall separating the nostrils is not centered. "According to various estimates, this occurs in about 22% to 50% of people," she said. "In most cases, the deviation is mild and does not significantly affect breathing. Even in these individuals, the nasal cycle functions normally and usually goes unnoticed because the body is able to physiologically balance airflow between the nostrils." However, conditions that increase nasal congestion, such as viral infections including influenza, allergic rhinitis and sinusitis, can make the nasal cycle much more noticeable. "In these situations, one nostril may feel especially blocked at certain times of the day, only for the sensation to reverse a few hours later as the other nostril becomes congested," she said. "In most cases, this is temporary and improves once the illness or allergy flare-up resolves." She added that anyone experiencing difficulty breathing through one nostril, whether it develops suddenly or gradually and does not improve within about two weeks, should consult an ear, nose and throat specialist. "If necessary, an endoscopic examination of the nasal cavity will be performed to identify the cause of the obstruction and determine the appropriate treatment," she said. What happens in the brain? Another study, published in Scientific Reports in 2022, examined the issue from a different angle by looking at brain activity rather than participants' subjective experiences. The study included 30 healthy adults ages 20 to 53. Researchers recorded their brain activity using a 64-channel electroencephalogram, or EEG, while participants breathed through one nostril and then the other. The study found that one-nostril breathing was associated with significant changes in brain activity compared with normal breathing. Breathing through the nondominant nostril was associated with reduced activity across all measured brain-wave frequencies. Breathing through the dominant nostril was linked to reduced activity in only some frequency bands, primarily alpha, beta and gamma waves. When researchers compared left- and right-nostril breathing, they found a somewhat different pattern. Breathing through the left nostril was associated with reduced brain activity across most frequency ranges, while breathing through the right nostril was associated with a less widespread reduction and relatively higher activity. The researchers noted that left-nostril breathing produced patterns resembling those observed during relaxation, rest and meditation, suggesting it may be associated with a calmer mental state. By contrast, right-nostril breathing appeared to be linked with greater physiological arousal. Here, too, the researchers emphasized that the findings are preliminary. They wrote that the relationship between one-nostril breathing and brain activity is complex and that additional research is needed to better understand the clinical significance of the findings. Taken together, the research paints an intriguing picture. On one hand, the nasal cycle is a well-documented, entirely normal physiological process that changes throughout the day and is influenced by sleep, breathing rate and body position. On the other, emerging evidence suggests that deliberately breathing through one nostril may be linked to measures of relaxation, stress, mind wandering and brain activity. Much more research, however, is needed before firm conclusions can be drawn.