Nose Breathing vs Mouth Breathing

What Is the Difference Between Nose Breathing and Mouth Breathing?

The difference between nose breathing and mouth breathing is the doorway air uses to enter the airways: nasal breathing draws air through the nostrils and the nasal cavity, while mouth breathing draws it straight through the oral cavity. Both paths meet in the pharynx, so from the throat downward the air follows the same route to the lungs.

The two doorways are built very differently. The nose opens into the nasal cavity, a narrow, curving chamber lined with moist mucous membrane and divided in two by the nasal septum. The oral cavity is wider and shorter, and its lining is built mainly for chewing, tasting and swallowing rather than for treating air. That design difference explains almost every other contrast on this page.

Explained simply

Think of the nose as an air conditioner with a dust filter, and the mouth as an open window. The air conditioner cleans, warms and moistens the air but lets it in more slowly. The open window lets in a lot of air quickly, but whatever is outside, cold, dry or dusty, comes straight in.

Is Nasal Breathing Better Than Mouth Breathing?

Yes, for everyday quiet breathing nasal breathing is better than mouth breathing, because the nose prepares air for the lungs and the mouth does very little of that work. Mouth breathing is not harmful in itself; it is the body's backup route for moments when the nose cannot supply enough air.

The verdict depends on the situation:

• At rest and during sleep: the nose wins. Air arrives cleaner, warmer and moister, and the mouth and throat stay moist.
• During hard exercise: the mouth wins on volume. Its low resistance lets a person move far more air per minute than the nose alone allows.
• With a blocked nose: the mouth is the only practical route, whether the cause is a cold, an allergy or the shape of the nose itself.
• While talking or singing: quick breaths are usually taken through the mouth between phrases, then let out slowly to make sound.

The table below sets the two routes side by side, feature by feature.

What Does the Nose Do to Air That the Mouth Cannot?

The nose filters, warms and humidifies inhaled air, adds nitric oxide from the sinuses and carries odors to the smell receptors, five jobs the mouth does poorly or not at all. Each job depends on structures found only in the nasal passages.

Filtering

Coarse hairs in the nasal vestibule catch large particles at the entrance. Farther in, three curled shelves of bone, the nasal conchae, split the airflow into narrow channels and make it swirl, so dust, pollen and microbes are thrown against sticky mucus. Most particles larger than about 10 micrometers are removed this way. The trapped material is carried back to the throat by beating cilia and swallowed, a system described on our cilia and mucus page.

Warming and humidifying

The lining of the nasal cavity is packed with blood vessels and kept wet by mucus. As air flows over this large, warm, moist surface, it gains heat and water vapor, so by the time it passes the throat it is much closer to body temperature and nearly saturated with moisture. On the way out, the cooler front of the nose takes back part of that heat and water, which helps the body conserve both.

Nitric oxide from the sinuses

The paranasal sinuses release nitric oxide gas into the nasal passages, and nasal breathing carries small amounts of it down into the lungs. Nitric oxide relaxes blood vessels and has antimicrobial effects, and researchers think this nasal supply may support airway defense and blood flow in the lungs. Mouth breathing bypasses this source.

Smell and protective reflexes

Only air drawn in through the nose sweeps odors up to the olfactory epithelium in the roof of the nasal cavity, which is why we sniff to sample a smell; see sense of smell. The nasal lining is also sensitive to irritants and can trigger a sneeze to blast them out before they travel deeper.

How Do Nose and Mouth Breathing Work Together?

Nose and mouth breathing work together as two entrances to one airway: both lead into the pharynx, feed the same lungs and are driven by the same breathing muscles, and the body can use either one or both at once. Whichever route the air takes, it then passes the larynx and trachea and reaches the same alveoli.

What they have in common

• Both are powered by the diaphragm and the intercostal muscles, which lower the pressure in the chest so air flows in.
• Both are run automatically by the breathing centers in the brainstem, and both can also be used on purpose.
• Both routes meet in the oropharynx, the part of the throat behind the mouth, and share the airway from there down.
• Neither changes how gas exchange works; oxygen crosses the same respiratory membrane either way.

Switching between routes

The lips, tongue and soft palate act as the switch. During quiet nasal breathing the lips are closed and the tongue rests against the roof of the mouth, sealing off the oral route. When more air is needed, the mouth opens and air flows through both routes at once, a pattern called oronasal breathing. Most people slide into oronasal breathing without noticing as activity rises.

The nasal cycle

Even in healthy people, one side of the nose is usually more congested than the other, and the sides swap every few hours. This normal nasal cycle lets each side rest and restore its moisture, and it is one reason a stuffy feeling can seem to move from one nostril to the other.

Nose Breathing vs Mouth Breathing During Exercise and Running

During exercise and running, most people breathe through the nose at low intensity and switch to combined nose and mouth breathing as the effort rises, because the nose cannot pass enough air for hard work. The point of the switch varies from person to person and depends on the size of the nasal passages, fitness and how congested the nose is.

At rest an adult breathes about 6 liters of air per minute, which the nose handles easily. During hard exercise the air breathed per minute can rise more than tenfold, and pulling all of it through the narrow nasal passages would take great effort from the breathing muscles. Opening the mouth removes most of that resistance. Studies of nose-only breathing during exercise show that it is possible at easy and moderate intensities, but it tends to limit the highest airflow a person can reach.

Mouth breathing during hard exercise has a cost too: cold, dry air reaches the lower airways with less conditioning. This is one reason sports in cold, dry air are linked to airway narrowing in people with asthma, a reaction known as exercise-induced bronchoconstriction.

Nose Breathing vs Mouth Breathing During Sleep

During sleep, nasal breathing is the normal pattern, and habitual mouth breathing at night is linked to snoring, a dry mouth on waking and lighter, more broken sleep. With the mouth closed, the jaw and tongue stay forward and help hold the throat open.

When the mouth falls open, the jaw drops back and the tongue can shift toward the back of the throat, narrowing the airway behind it. The soft tissues there may then flutter as air passes, which is the sound of snoring. Breathing through the mouth all night also dries out saliva, which normally protects the teeth and gums, so people who mouth breathe at night more often wake with a dry mouth, bad breath or irritated gums.

Night-time mouth breathing is often a sign rather than a cause: it usually means the nose is narrowed by congestion, enlarged adenoids or a deviated septum. Loud snoring with pauses in breathing can point to obstructive sleep apnea, in which the throat repeatedly collapses during sleep.

Can Mouth Breathing Change Face Shape?

Long-term mouth breathing in childhood has been associated with changes in face shape, including a longer lower face, a narrow upper jaw and crowded teeth, but the link is debated and genes play a large part. In adults, whose facial bones have finished growing, mouth breathing does not reshape the face in the same way.

While a child's face is still growing, the resting position of the lips, tongue and jaw influences how the bones develop. In habitual nasal breathing the tongue rests against the palate and helps widen the upper jaw. In habitual mouth breathing the jaw hangs open and the tongue sits low, and researchers have described a pattern sometimes called adenoid facies or long face syndrome: open lips at rest, a high, narrow palate and a longer lower face. Enlarged adenoids or tonsils that block the nasal airway are a common cause of this kind of mouth breathing in children.

Most studies behind this pattern show an association, not proof of cause, and faces vary widely for reasons that have nothing to do with breathing. Dentists and orthodontists often take breathing habits into account when they look at how a child's jaws are developing.

Why Do Some People Breathe Through Their Mouth?

People breathe through the mouth mainly when the nasal airway is narrowed or blocked, either briefly, as during a cold, or long term, because of the structure of the nose and throat. Common causes include:

• Colds and allergies: swelling of the nasal lining and extra mucus narrow the passages.
• Sinusitis: inflamed sinuses and thick mucus can block drainage and airflow.
• Deviated septum: a septum bent to one side narrows one or both nasal passages.
• Enlarged turbinates: swollen inferior nasal conchae reduce the space for air.
• Enlarged adenoids and tonsils: especially in children, these can block the back of the nose and the throat.
• Habit: some people keep breathing through the mouth after the original blockage has cleared.

Newborn babies are the opposite case. For their first months they are strongly preferential nose breathers, partly because the larynx sits high in the neck and the epiglottis nearly touches the soft palate, so a blocked nose troubles them more than it troubles older children. Our respiratory diseases section covers these conditions, and anyone with lasting breathing problems should see a doctor.