Tip · Breathing

Breathing Only Through the Nose

Q: What exactly is established about nasal breathing?

That the paranasal sinuses release nitric oxide and this gas reaches the lungs during inhalation has been measured. In healthy children the NO concentration in nasal air was 221 ppb, in children with Kartagener syndrome practically zero. It is also established that the nose warms and humidifies the inhaled air and that a blocked nose measurably worsens breathing at night. Everything beyond that is far less well supported.

Q: Does nasal breathing improve my endurance?

According to the available data, probably not. In a cardiopulmonary exercise testing study, exclusively nasal breathing significantly lowered maximal oxygen uptake, ventilation and the power output achieved in watts, and increased perceived exertion. In well-trained endurance athletes, there was no significant difference in VO2max and maximal power output between mouth breathing and nasal-plus-mouth breathing.

Q: Should I tape my mouth shut at night?

The entire literature on this comprises ten studies with a total of 213 patients, and they had mouth breathing or sleep apnea, not simply poor sleep. Two of these studies found an improvement in sleep apnea markers, the rest no difference. The authors of the systematic review explicitly warn of a risk of suffocation with impaired nasal breathing.

Q: How can I tell that mouth tape would be risky for me?

Any form of impaired nasal breathing is a reason for exclusion, that is, a cold, allergy, nasal polyps or a deviated septum. According to meta-analysis, nasal obstruction increases the apnea-hypopnea index by 13.78 events per hour and can produce sleep-apnea-like abnormalities in previously healthy people. Anyone who snores and has pauses in breathing should have this examined first.

Q: Does nasal breathing help with asthma or exercise-induced asthma?

There are two early small studies with five and twelve asthma patients respectively, in which nasal breathing during exercise attenuated the subsequent bronchoconstriction. Whether this was due to nitric oxide or to the moister inhaled air has not been clarified. For COPD patients, by contrast, nasal breathing during exercise is explicitly not recommended, because air hunger and hypoventilation can worsen the symptoms.

Q: Is the nitric oxide effect noticeably relevant for a healthy person?

It is greatest where it is lacking. In long-term ventilated patients, arterial oxygen partial pressure rose by 18 percent when they were supplied with air from their own nose. In healthy people, the difference in transcutaneous oxygen partial pressure was 10 percent, and even that only in six of eight subjects. The authoritative review describes these effects in healthy people as very small and their clinical significance as unclear.

The nose humidifies, filters and supplies nitric oxide – that is established. The promises about sleep and endurance are not.

Breathing only through the nose is not a technique but the normal state. It becomes interesting because the nose does more than let air through: it releases nitric oxide, warms and humidifies. That is established. The promises attached to it — better sleep, more endurance — are not.

In short

That exhaled nitric oxide comes overwhelmingly from the paranasal sinuses and reaches the lungs during inhalation has been cleanly measured. The benefit is greatest where the gas is lacking: in long-term ventilated patients, arterial oxygen partial pressure rose by 18%; in healthy people the difference in transcutaneous oxygen partial pressure was 10%, and even that only in six of eight subjects. For endurance there is no supporting evidence, but evidence to the contrary: in cardiopulmonary exercise testing, exclusive nasal breathing significantly lowered maximal oxygen uptake, ventilation and power output in watts. For mouth taping at night, the data are thin and the risk is real.

What is behind it

The paranasal sinuses continuously produce nitric oxide and release it into the nasal cavity. How clear-cut this is becomes apparent in the comparison with Kartagener syndrome: nasal air of affected children contained practically no NO (4 ± 1 ppb) versus 221 ± 14 ppb in age-matched controls — a reduction of 98%.

Added to this is the mechanical part: the nose warms, humidifies and filters the inhaled air. This is one of the reasons why nasal breathing during exercise attenuates exercise-induced bronchoconstriction — whether this is due to NO or to the moister air, the authors of the authoritative review explicitly leave open.

How it works

NO is a vasodilator and a mild bronchodilator; it is thought to act as an aerocrine messenger that selectively dilates the vessels of well-ventilated lung regions and thereby improves gas exchange. The downside is resistance: healthy adults spontaneously switch to combined nasal and mouth breathing as soon as minute ventilation reaches about 35 to 45 liters per minute, and without training they can sustain exclusive nasal breathing only up to about 80% of maximal oxygen uptake.

Mouth tape: the point with the greatest potential for harm

Taping the mouth shut at night is the most popular and at the same time the most poorly supported part of the topic. The entire literature comprises ten studies with a total of 213 patients — and these patients had mouth breathing, sleep-related breathing disorders or sleep apnea, not simply the wish for better sleep. Two studies showed a significant improvement in established sleep apnea markers, the rest no difference. A scoping review screened 177 papers, of which nine met the criteria, and found little consensus.

The risk, by contrast, is concretely named: asphyxia in the presence of nasal obstruction. Many studies excluded people with nasal obstruction or nasal pathology from the outset — so the results apply precisely not to the group for whom it becomes dangerous.

What is well supported

Three things hold up: the origin of nitric oxide, with 221 ± 14 ppb in the nasal air of healthy children versus 4 ± 1 ppb in Kartagener syndrome; the physiological effect of this NO; and that impaired nasal breathing measurably worsens breathing at night. In a meta-analysis, experimentally or surgically induced nasal obstruction was associated with an increase in the apnea-hypopnea index of 13.78 events per hour and in the oxygen desaturation index of 7.45 events per hour; mean saturation fell by 0.70% and minimum saturation by 1.75%.

What the studies show

Where the NO comes from (Lundberg et al. 1994 and 1996)

The second paper tested in three stages whether the inhaled NO has an effect: in healthy people, a 10% higher transcutaneous oxygen partial pressure in six of eight subjects; in long-term ventilated patients, an 18% higher arterial oxygen partial pressure in six of six; in short-term ventilated patients, an 11% lower pulmonary vascular resistance index in four of twelve.

The critical assessment (Illidi et al. 2023)

Conclusion of the currently best summary: nasal breathing can improve arterial oxygenation in critically ill patients at rest, but there is little evidence that this carries over to healthy people. During submaximal exercise it is feasible, and after extensive habituation even at maximal exercise — for a performance benefit in healthy people there are few to no data.

At the performance limit (Mapelli et al. 2025)

Twelve healthy people completed four maximal cardiopulmonary exercise tests with an identical ramp protocol within one month: standard, exclusively nasal, exclusively oral, partially nasal with one nostril blocked. Compared with all other conditions, exclusively nasal breathing was associated with significantly lower maximal oxygen uptake, ventilation, breathing rate and power output in watts (each p < 0.05), and perceived exertion was higher in all phases.

The mouth tape review (Rhee et al. 2025)

Systematic review according to PRISMA: 120 articles reviewed, 86 screened, 24 assessed in full text, 10 included with a total of 213 patients. The authors see a potentially serious risk of harm for people who practice this trend indiscriminately.

Where the data stop

The NO effect in healthy people is small: 10% higher transcutaneous oxygen partial pressure, and that only in six of eight subjects; the authoritative review calls the effects in healthy people very small and their clinical significance unclear. For endurance, it is not only evidence of a benefit that is missing; there is evidence of a disadvantage. In twelve well-trained endurance athletes, the breathing mode made no significant difference to VO2max and maximal power output.

The gap is largest for sleep. The most positive mouth tape study is small and unblinded: 20 mouth breathers with mild obstructive sleep apnea, one week of hypoallergenic silicone tape, 13 of 20 (65%) were considered responders, the mean apnea-hypopnea index fell from 8.3 to 4.7 events per hour, the snoring index from 303.8 to 121.1, and minimum saturation rose from 82.5% to 87%. Without a control group, without blinding, only in mild sleep apnea and only in people who tolerated the taping. On vascular effects, there is so far only one observational study in 45 young healthy men.

How to do it

In the investigations of NO and vascular function, participants breathed exclusively through the nose at rest, compared with exclusively through the mouth. During exercise, the spontaneous switch to mouth breathing occurs at a minute ventilation of about 35 to 45 liters per minute, and without training, exclusive nasal breathing can be maintained only up to about 80% of maximal oxygen uptake. After a habituation phase of more than six months it is possible even at maximal intensity, without VO2max suffering. Anyone chasing personal bests is, according to these data, nonetheless better off breathing oronasally or orally.

Safety

Conscious nasal breathing during the day is practically risk-free. The risk lies with mouth tape at night, and there it is concrete. Any form of impaired nasal breathing is a reason for exclusion: a cold, allergy, nasal polyps, a deviated septum. Anyone who tapes their mouth shut with a blocked nose combines two effects that reinforce each other — nasal obstruction raises the apnea-hypopnea index by 13.78 events per hour according to meta-analysis and can cause sleep-apnea-like abnormalities in previously healthy people. Snoring with observed pauses in breathing, daytime sleepiness or morning headaches are a reason for a sleep study, not for a strip of tape: a taped mouth dampens the symptom without touching the cause. There are no data for children, and with anything that dampens the arousal response — alcohol, sleeping pills, sedatives — the protective mechanism that would open the mouth when short of air is lost. For COPD patients, nasal breathing during exercise is explicitly not recommended.

BK-Score Thin human evidence

Human evidence		5
Mechanism		7
Safety data		9
Hype gap		6
Track record of use		10

That the paranasal sinuses release nitric oxide and the nose humidifies and filters the inhaled air is established. The further-reaching promises – better sleep, more endurance – rest on small studies and self-reports.

The score rates the state of knowledge, not the effect. “Safety data 9” means well studied – not harmless.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)

Frequently asked questions about Breathing Only Through the Nose

What exactly is established about nasal breathing?