12 very good reasons to never breath through the mouth again

mouth breathing - comic

Breathing through the mouth doesn’t just give you a stupid look on your face. When it comes to breathing, the nose is an asset that should never be bypassed. The mouth comes useful for drinking, eating, speaking, maybe singing or even kissing… anyway, it has never been designed for air flow management.

Just have a look at animals: they all breathe through the nostrils (apart from the dog that can turn its mouth into a cooling system, but humans are not capable of it. Or did I miss something?). Moreover, a farmer will immediately identify an animal that breathes through the mouth, which is always an alarming sign of poor health.

shut the mouth - comic

Whether it’s for inhaling, exhaling, sleeping or doing sports, the nose is always the right pipe. Let’s see why.

Mouth breathing dries your mouth

This doesn’t seem to be a big concern. And yet! The mouth constantly produces saliva. If you use your mouth to breathe, the production of saliva is dried out and does not supply the stomach. As opposed to what some might think, saliva plays a constant role for the stomach: even when the stomach is empty! Saliva does play a role of maintenance and cleaning.

The nose is a filter

The nose can filter air particles, especially thanks to its hairs. That prevents pollen, for example, from entering the lungs. A study showed that a density of hair in the nose that is too low will increase the risk of asthma1.

Cyrano de Bergerac
Cyrano de bergerac, famous for his nose, was probably healthy: p

The nose warms up the air

An air that is too cold represents an aggression for the lungs. Since the nasal cavities are longer and the nasal breathing is generally slower, it will better heat the air that enters the lungs.

the nose warms the air better than the mouth - comic

The nose moisten the air

Just like for the cold, an air that is too dry is not good for the lungs. The nose helps to moisten the inhaled air. And this moisture is not completely lost: by also exhaling through the nose, the latter is also able to collect some of it back.

Nitric Oxide ( NO )

The sinuses release a gas, called nitric oxide ( NO ), which get mixed with the air we breathe2. This gas plays two important roles.

NO: a protective gas

The NO, which has been believe to be toxic for a long time, actually sterilizes the inhaled air by killing or weakening the bacterias and viruses that enter the lungs. It therefore eliminates potentially harmful bacterias such as Salmonella or Shigella. This will protect the lungs from the inflammations caused by these pathogens.

nitric oxide: a protective gas - comic

So logically, when someone is sick (flu or cold), you are more likely to be contaminated if you are breathing through the mouth.

NO: a dilating gas

NO is used in medicine to expand the arteries (vaso-dilator) and decrease the blood pressure. When inhaled, it dilates the arteries in the alveoli, maximizing the penetration of oxygen into the blood .

NO - gas dilator - comic

Humming: the super power of the monks

It has been observed that doing long “Hummmmmm” (like monks and other weird people) makes it possible to temporarily increase (for about 15 minutes) the production of NO4.

The lung-to-nose path is longer than the lung-to-mouth path

“So?” will you tell me. Well, when we breathe, we usually keep a certain amount of air in the lungs: they never get completely empty. This ensures that the air mixture (old + new air) keeps an acceptable temperature and moist, and enables to maintain of a certain concentration of the famous NO gas that we’ve seen previously.

So: when you exhale, some of the air goes up to the nose but does not come out of the body. This air plays the same role as the air that remained in the lungs because it stays warm, moist and does not change its composition. On the contrary, breathing through the mouth decreases the amount of air that remains in the body between two breaths.

Immune system

When breathing through the nose, the filtered particles are trapped in some mucus. The latter then goes down into the stomach: the pathogens that it contains will then be killed or weakened by enzymes and chloridic acid. Once weakened, these viruses or bacterias will enter the small intestine and will be identified by the immune system (via the same process as the vaccine).


When the intensity of exercises remains relatively moderate, it is quite possible to breathe only through the nose during sport. A study of a low-intensity exercises found that participants breathing through the nose used a slightly smaller amount of air in the lungs (tidal volume) and a much lower respiratory rate5. This suggests that nasal breathing allows better penetration of oxygen into the blood. Thank you NO!

Sport increases the respiratory rate. If you breathe through the mouth, the problems seen above will increase: dry mouth, dry and cold air in the lungs… And if you sport in a polluted city or near some fields covered with pesticides…

A study from 2011, with cycling Swedish folks

A Swedish study6 from 2011 on 10 people showed significant results. The subjects did 30 minutes of biking, breathing only through the mouth. Then they did it again two days later, but breathing only through the nose. And so on, for 3 weeks.

conscious breathing nasal vs mouth study - biking with scotch on mouth or nose

Results of nasal breathing (compared to mouth breathing):

  • 11% reduction in lactic acid
  • an average of 22 fewer breaths (for the same effort over 30 minutes) (up to 31% reduction for one subject)
  • 4 out of the 10 subjects were able to ride with a higher intensity
  • Clas Björling, a Swedish former triathlon record holder, showed a 38% lactic acid reduction and a heart rate 10% slower
  • one of the subjects had an asthma attack when he breathed through the mouth, while he had no problem breathing through the nose

Note: when idle, breathing represents 3 to 5% of the body energy consumption. Breathing through the nose decreases the number of breaths and therefore slightly reduces our energy consumption.

After this study, all participants agreed that they intended to use nasal breathing as much as possible, either at rest or during exercise, because it seemed more natural.

There’s more…

Carbon monoxide and cigarettes

A study on smokers have shown that the nose is able to filter carbon monoxide. After smoking a cigarette, those who breathed through the mouth rejected CO, while those who breathed through the nose didn’t. 7. Surely, this is focused on the filtration of the air that comes out and not the air that goes in, but I allow myself to assume that it works both ways. And knowing that carbon monoxide is a very toxic gas, it is not a small thing!

co smoked: nose vs mouth - diagram

smoking by the nose - comic

Poor brain ventilation

Similarities have been observed in the brain between children who breathe through the mouth and adults who do sleep apnea8.

The nervous system

In mice, mouth breathing causes acidosis (blood becomes too acidic), which indirectly disrupts the activity of the central nervous system9 (which mainly includes the brains).


In some subjects, the mere fact of being forced to breathe through the mouth is enough to trigger an asthma attack10. Oral breathing is also suspected to be the cause of some acute exacerbations of asthma.

The solutions

If you find yourself breathing through the mouth, the first thing to do is shut it up! Take some time and concentrate on a calm and nasal breath, and anchor this mechanism (it is a form of meditation). Re-learn how to breathe!

If the problem occurs at night, it is a little bit more complicated. Some testify that a simple scotch on the mouth is enough to correct the problem (to be tested). Otherwise, there are some nostril dilators, such as the “Nozovent“, which seem to be quite effective :

  • reduction of asthma at night11
  • decreased snoring and fatigue at wake up time12
  • improved arterial oxygen saturation during sleep apnea13


As for dentures, they do not seem to work that well14



Not long ago, I wouldn’t have suspected that breathing through the mouth could be the source of so many problems. The air we breathe contains many elements that represent a stress for the lungs: it is often cold, dry, full of viruses, bacteria, pollen, chemicals… The nose is a very powerful asset and we must take advantage of it at all times! I am 100% convinced and I will try to breathe through the nose as much as possible!

And you? Does this article change your idea of breathing? Leave a message in the comments!

  1. Does nasal hair (vibrissae) affect the risk of developing asthma in patients with seasonal rhinitis?
  2. Primarily nasal Origin of Exhaled nitric oxide and Kartagener’s syndrome lack in
  3. Humming Greatly Increases Nasal Nitric Oxide[ /note]. Impressive, right? I guess you don’t feel like mocking anymore and you may even want to try this funny technique!

    humming - comic

    Good to know: it does not work if you have a sinus obstruction3 Humming-induced release of nasal nitric oxide for assessment of sinus obstruction in allergic rhinitis: pilot study.

  4. Comparison of maximal oxygen consumption with oral and nasal breathing.
  5. Pilot study – nasal vs. mouth breathing
  6. Nitric oxide but not carbon monoxide is released in the human nasal airways
  7. Mouth breathing children have cephalometric patterns similar to those of adult patients with obstructive sleep apnea syndrome.
  8. Mouth breathing increases the pentylenetetrazole-induced seizure threshold in mice: a role for ATP- sensitive potassium channels.
  9. Enforced mouth breathing decreases lung function in mild asthmatics.
  10. Reduced nocturnal asthma asthma by improved nasal breathing.
  11. Improved nasal breathing reduces snoring and morning tiredness. A 6-month follow-up study.
  12. Increased nasal breathing decreases during sleep apnea.
  13. Obligatory nasal breathing: effects are snoring and sleep apnea.
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