You can breathe through your nose and mouth at the same time, and in fact you do it far more often than you probably realize. During conversation, most of your breaths are simultaneous nasal-oral inhalations, and during moderate-to-hard exercise the split becomes even more pronounced. The key player is a flap of tissue at the back of your mouth called the soft palate, which acts as a valve deciding how much air goes through each route. The mechanics of how it works, when it switches modes, and why the breathing route matters for your health are more interesting than the simple yes-or-no answer suggests.
The Soft Palate Runs the Show
The reason you can route air through your nose, your mouth, or both comes down to a single piece of anatomy: the soft palate, also called the velum. It sits at the back of the roof of your mouth, behind the hard bony palate you can feel with your tongue. Unlike most structures in your airway, the soft palate is muscular and highly mobile. It can swing upward to seal off your nasal passages, drop downward to seal off your mouth from the throat, or rest in an intermediate position that leaves both pathways open at once.
A 2025 narrative review describes the soft palate as a “complex anatomical structure” capable of “dynamically creating valve closure of the nasal and the oral cavities,” with its precise movement being critical for speech, swallowing, and respiration.1PubMed. Anatomy of the Soft Palate and Its Role in Upper Airway Function: A Narrative Review The mechanism that accomplishes this is sometimes called the velopharyngeal mechanism, referring to the coordinated action of the velum and the walls of the pharynx (the shared space at the back of your throat). Together, they create a tight seal that can separate the oral and nasal cavities on demand.2PubMed. Anatomy and physiology of the velopharyngeal mechanism
What makes this valve interesting is that it has more than two settings. It is not a binary switch toggling between “nose open” and “mouth open.” A fluoroscopy study of healthy volunteers showed three distinct configurations: during quiet breathing, the soft palate closed the oral pathway entirely, producing pure nasal breathing; during forced exhalation efforts, it sealed the nasal side, routing all air through the mouth; and during oronasal breathing, the soft palate simply hovered in a middle position between the tongue and the back wall of the throat, letting air flow through both routes simultaneously.3PubMed. Soft palate and oronasal breathing in humans That middle position is what lets you breathe through both passages at once, and it turns out to be the default mode in a surprising number of everyday situations.
How Airflow Actually Splits
When both routes are open, air does not flow equally through your nose and mouth. The split depends on what you are doing, how hard you are breathing, and the anatomy of your particular nasal passages. But researchers have measured this split with partitioned masks that capture nasal and oral airflow independently, and the results paint a clear picture.
During speech, simultaneous nasal-oral breathing is the rule, not the exception. A study that measured inspiratory patterns during counting, paragraph reading, spontaneous talking, and conversation found that the predominant pattern in all four tasks was simultaneous nasal and oral inspiration. For counting, the group average was 100 percent simultaneous breaths; even during casual conversation, it was about 84 percent.4PubMed Central. Nasal and Oral Inspiration During Natural Speech Breathing In other words, nearly every breath you take while talking enters through both your nose and your mouth at the same time. Most people have no awareness of this. It happens automatically because your soft palate drops to the intermediate position when your mouth is open for speech, and air simply takes both available paths.
Clinical recordings using instruments that separately track nasal and oral airflow confirm that the breathing patterns vary from person to person and moment to moment. Some people breathe exclusively through the nose, some exclusively through the mouth, and many show a mixed pattern within the same recording session.5PubMed. A new approach to studying the nasal and oral breathing routes The soft palate’s resting position, the degree of nasal congestion, and habitual patterns all influence which mode predominates. But the capacity for simultaneous breathing is universal in healthy adults, even if the default resting pattern differs.
What Changes During Exercise
If you have ever noticed that you start breathing through your mouth partway through a run, you are not imagining it. There is a well-documented ventilatory threshold at which most people switch from nose-only breathing to oronasal breathing. A study of 30 subjects found that the majority switched from nasal to oronasal breathing at a ventilation rate of roughly 35 liters per minute.6PubMed. Oronasal distribution of respiratory airflow For context, quiet breathing at rest involves roughly 6 to 8 liters per minute, so the switchover point corresponds to moderate exercise, around the level of a steady jog for most people.
After the switch happened, the nose did not shut down. Instead, the nasal portion dropped suddenly to about 57 percent of total airflow, with the mouth picking up the rest. As exercise intensity climbed further, the mouth’s share grew rapidly. At around 45 liters per minute, nose and mouth were contributing equally. At very high ventilation rates near 90 liters per minute, the mouth handled about 61 percent of total airflow while the nose still carried the remaining 39 percent.6PubMed. Oronasal distribution of respiratory airflow So during hard exercise, you are very much breathing through both passages, with the mouth gradually taking on a larger share as the demand increases.
Not everyone follows this pattern identically. The same study identified a minority of subjects who were habitual mouth breathers at all ventilation levels, and another group of persistent nose breathers who maintained nasal-only breathing even during exertion. These outliers accounted for roughly a third of the subjects. Your own pattern depends partly on habit, partly on your nasal anatomy, and partly on whether you have any nasal obstruction.
Why the Breathing Route Matters for Your Lungs
The nose does more than just provide a passage for air. It warms, humidifies, and filters incoming air before it reaches the lungs, and it does this with surprising efficiency. A computational simulation of upper airway thermodynamics found that at moderate flow rates, the nasal cavity achieved heating and humidification efficiencies of roughly 86 to 88 percent and 91 to 93 percent, respectively. That was about 1.6 to 1.8 times higher than what oral breathing achieved, which managed only 50 to 51 percent heating efficiency and 53 to 57 percent humidification.7International Journal of Thermal Sciences. Anatomically-trained patient-specific in-silico simulations for predicting thermo-regulation and humidification in human body upper respiratory pathways Both efficiencies declined at higher airflow, which helps explain why breathing through your mouth during hard exercise can leave your throat feeling dry and raw: the mouth simply cannot condition air as well as the nose can.
There is also a chemical advantage to nasal breathing. Your paranasal sinuses produce nitric oxide, a gas that, when inhaled through the nose, reaches the lungs and acts as a mild vasodilator, opening blood vessels in the lung tissue. A study in healthy subjects found that blood oxygen levels measured through the skin were about 10 percent higher during nasal breathing compared to oral breathing.8PubMed. Inhalation of nasally derived nitric oxide modulates pulmonary function in humans In intubated patients who could not breathe through their nose at all, adding nasal air samples to their ventilator supply increased arterial oxygen levels by 18 percent and reduced pulmonary vascular resistance in some patients. A follow-up study in cardiac surgery patients confirmed that nasal breathing produced lower pulmonary vascular resistance compared to mouth breathing, supporting the idea that self-inhaled nitric oxide from the sinuses actively modulates lung blood flow during normal breathing.9PubMed. Decreased pulmonary vascular resistance during nasal breathing: modulation by endogenous nitric oxide from the paranasal sinuses
This is part of why the recent popular emphasis on nasal breathing has some physiological legitimacy. When you breathe through both nose and mouth simultaneously, the nasal portion of airflow still delivers nitric oxide and still conditions the air passing through it. But the oral portion arrives cooler, drier, and without the nitric oxide boost. During simultaneous breathing, you get a blend of both, which is better than pure mouth breathing but not as optimal for conditioning as nose-only breathing would be.
What Happens During Sleep
Sleep is where the breathing route has arguably its biggest practical impact. During sleep, muscle tone throughout the airway drops, and the soft palate tends to relax backward. If you end up breathing primarily through your mouth while asleep, the consequences go beyond a dry throat in the morning.
A study measuring upper airway resistance during sleep found that resistance was significantly higher during oral breathing than nasal breathing, even when controlling for sleep stage and body position. The median airway resistance during oral breathing was roughly 12 cmHâ‚‚O per liter per second, compared to about 5 during nasal breathing. More strikingly, the frequency of airway obstruction events was dramatically higher during oral breathing: the average apnea-hypopnea index (a measure of how many times breathing partially or fully stops per hour) was 43 during oral breathing versus just 1.5 during nasal breathing.10European Respiratory Journal. Effect of nasal or oral breathing route on upper airway resistance during sleep That is the difference between severe obstructive sleep apnea and essentially normal breathing.
The mechanism is partly structural. Computational fluid dynamics modeling of patients with obstructive sleep apnea showed that oral breathing generated significantly more negative pressure in the upper airway than nasal breathing, whether the mouth was open or closed during nasal breathing.11PubMed Central. The effect of nasal and oral breathing on airway collapsibility in patients with obstructive sleep apnea: Computational fluid dynamics analyses Greater negative pressure during inhalation means the airway is being sucked inward more forcefully, making it more likely to collapse. Nasal breathing, by contrast, generates a gentler, more even pressure profile that helps keep the airway open. This is one reason why mouth-taping during sleep has gained attention, though the evidence for that particular intervention is still evolving.
When the Valve Does Not Work Properly
Some people cannot fully seal off the nasal or oral passage, and for them, simultaneous nasal-oral airflow is not a choice but a constant, unwanted condition. This is called velopharyngeal insufficiency, and it means the soft palate cannot close tightly enough against the pharyngeal walls. The result is that air leaks through the nose during speech sounds that should be entirely oral, producing hypernasal speech and, in some cases, difficulty building up pressure for certain consonants.
Velopharyngeal insufficiency is most commonly associated with cleft palate, but it can also stem from neurological conditions. A series of 32 cases found that causes included muscular diseases and damage to the nerve pathways controlling the palate’s movement, including cases where bilateral dysfunction of nerve tracts controlling the throat produced what is known as pseudobulbar palsy.12Developmental Medicine & Child Neurology. Velopharyngeal Insufficiency: the Neurological Perspective. A Report of 32 Cases Stroke, traumatic brain injury, and certain progressive neurological diseases can all impair the palate’s function. For these patients, the inability to properly control the soft palate valve is a daily functional challenge affecting eating, drinking, and communication.
The speech effects are measurable. When researchers estimated the amount of nasal sound energy during production of stop consonants (sounds like “b,” “d,” and “g” that should involve no nasal airflow), even healthy speakers showed some nasal energy, with peak nasalance values ranging from 20 to 80 percent across individuals.13PubMed. Estimation of transpalatal nasalance during production of voiced stop consonants by noncleft speakers using an oral-nasal mask Some of this is just acoustic energy transferring through tissue rather than actual air leakage, but it demonstrates that the seal between oral and nasal cavities is never perfectly airtight, even in people with normal anatomy. The system operates on “good enough” rather than hermetic closure.
Why Babies Are Different
If you have spent time around a newborn with a stuffy nose, you may have noticed how distressed they become. Human newborns are considered obligate nasal breathers, meaning they breathe through the nose almost exclusively and have great difficulty switching to mouth breathing when the nose is blocked.14PubMed Central. It takes a mouth to eat and a nose to breathe: abnormal oral respiration affects neonates’ oral competence and systemic adaptation The effects of nasal obstruction in infants can be severe and sometimes persist into later life.
The reason newborns are locked into nasal breathing relates to the anatomy of their throat. In infants, the larynx sits much higher in the neck than in adults, and the epiglottis can interlock with the soft palate, creating a direct channel from the nose to the lungs that bypasses the mouth. This arrangement has a major advantage: it allows babies to breathe and swallow milk at the same time without choking, something adults cannot do. But the tradeoff is that mouth breathing is not readily available as a backup. As the larynx descends during the first year or two of life, the adult configuration develops, and the child gains the ability to voluntarily route air through either the nose, the mouth, or both.
This developmental shift is why simultaneous nose-and-mouth breathing is an adult skill that develops gradually. By adulthood, the soft palate and velopharyngeal mechanism have matured enough to fluidly switch between configurations hundreds of times per day, often without any conscious awareness.
The Swallowing Interruption
One thing you absolutely cannot do is breathe through either route while swallowing. Swallowing temporarily converts the shared pharyngeal space from an airway into a food channel. During the pharyngeal phase of swallowing, the soft palate rises to seal off the nasal cavity from above, and the larynx closes from below, completely shutting down the airway for a fraction of a second.15PubMed Central. Coordination of Mastication, Swallowing and Breathing This dual closure is what prevents food and liquid from entering the nasal passages or the lungs. The timing has to be precise, because between swallows during a meal, the pharynx switches back to airway mode just long enough for a breath before the next swallow begins.
People who have neurological damage affecting the coordination of swallowing and breathing are at risk of aspiration, where food or liquid enters the airway. This is the same velopharyngeal mechanism that controls nose-vs-mouth airflow, just operating in its most critical mode. The fact that a single anatomical valve handles both breathing-route selection and airway protection during swallowing helps explain why disorders of the soft palate can have consequences far beyond speech.
How Breathing Route Connects to Flavor Perception
There is a lesser-known sensory dimension to nasal-oral airflow that comes into play every time you eat or drink. Much of what people call “taste” is actually smell, delivered by air flowing from the back of the mouth up through the nasal passages from below. This retronasal route, as opposed to the orthonasal route of sniffing something directly, is synchronized with exhalation during chewing and swallowing.
The timing matters. A study that manipulated whether odors arrived via the retronasal route (synchronized with exhalation, as happens during eating) or the orthonasal route (synchronized with inhalation, as happens during sniffing) found that taste intensity ratings were significantly higher when the smell arrived retronasally.16PubMed Central. Taste of breath: the temporal order of taste and smell synchronized with breathing as a determinant for taste and olfactory integration Your brain integrates the retronasal smell signal with what your tongue is detecting and reports the result as a single, richer taste experience. This is only possible because air moves from the oral cavity into the nasal cavity during exhalation, a form of simultaneous oral-nasal airflow in reverse. If you have ever noticed that food tastes bland when your nose is congested, this is the mechanism you are missing.
The connection to breathing route is direct: when you exhale during a meal, some air travels out through the nose carrying volatile compounds from the food in your mouth. A completely sealed-off nasal passage, whether from congestion or from the soft palate being locked in the wrong position, eliminates this pathway and flattens flavor perception. The same soft palate dynamics that control whether you breathe through your nose, your mouth, or both during a run are also quietly shaping how your dinner tastes.