Nose breathing v mouth breathing: what the evidence says

What your nose does

Your nose is not just a passage for air. As air flows through it, past the folds inside and over the moist, sticky lining, it is:

• Warmed towards body temperature, even on a cold day.
• Moistened, so it doesn’t dry out your airways.
• Filtered, as hairs and mucus trap dust, pollen and some germs.
• Slowed, because the nose resists airflow more than the mouth, which tends to make breathing slower and calmer.

Your sinuses also make nitric oxide, a gas that widens blood vessels and has anti-germ effects. When you breathe in through your nose, some of it travels down to your lungs. When you hum, the amount in your nose rises around 15-fold. See humming breath.

When mouth breathing is normal

You naturally switch to mouth breathing when you need more air than your nose can supply, such as during hard exercise, or when your nose is blocked by a cold, hay fever or a deviated septum. That is fine. There is no good evidence that forcing yourself to breathe through your nose at high exercise intensities improves performance.

When mouth breathing is a problem

Breathing through your mouth most of the time, especially at night, can leave you with a dry mouth and throat, and is linked with snoring. In children, constant mouth breathing with loud snoring can be a sign of enlarged adenoids or tonsils. In adults, loud snoring with pauses in breathing, or feeling very sleepy in the day, can be a sign of sleep apnoea. These are worth seeing your GP about, because they can be treated.

What the research shows

The effects of the nose on air temperature, moisture and filtering are well established physiology. Beyond that, the evidence is patchier. Nose breathing is a central part of Buteyko breathing and NHS breathing retraining for asthma, and trials of those programmes found fewer symptoms, but they changed several things at once, so the effect of nose breathing alone isn’t known.

Claims that nose breathing transforms sleep, focus, jaw shape or athletic performance mostly come from books and social media rather than trials.

What about mouth taping?

Taping your lips together at night to force nose breathing has become a social media trend. A 2025 systematic review found 10 studies with 213 people in total. Two found improvements in markers of sleep apnoea; the rest found no difference, and the reviewers warned of a potentially serious risk, including suffocation if the nose becomes blocked. We don’t recommend it. If you think you mouth-breathe at night, see your GP, who can look for a cause such as a blocked nose or sleep apnoea.

Making nose breathing easier

• Practise breathing through your nose during the day, gently and quietly, while sitting, walking and reading.
• Treat a blocked nose: saline rinses and, for hay fever, a steroid nasal spray from a pharmacist can help.
• Use diaphragmatic breathing and resonance breathing, which are usually done through the nose.