Nasal breathing vs. mouth breathing: what changes while you sleep

For most people, nasal breathing is better than mouth breathing during sleep. Your nose filters, warms and humidifies the air and adds a little nitric oxide from your sinuses, and in sleep lab studies the airway met less resistance when people breathed through it. That's why healthy people with a clear nose breathe through it almost all night.

What your nose does that your mouth doesn't

Nose hairs and mucus trap dust, pollen and other particles before they get further in. Cleveland Clinic describes mucus as the body's way of trapping dirt, germs and other particles, which you then swallow during the day. The air also warms up toward body temperature and picks up moisture, which is easier on your throat and airways. And your sinuses produce nitric oxide, which you breathe in along with the air when you breathe through your nose.

The warming and moistening happens fast. A 2000 study in Rhinology measured temperature and humidity at different points inside the noses of 23 volunteers. Most of the rise happened in the front part of the nose, within a short distance of the nostrils, and the further increase deeper in was smaller.

How much do people breathe through their mouth during sleep?

Less than you might think, if the nose is clear. In a 2003 study in the Journal of Applied Physiology, researchers fitted 10 healthy adults with normal nasal resistance with a mask that measured the nose and mouth separately. While they were asleep, the mouth carried about 4% of the air they breathed in. That share didn't change between light sleep, deep sleep and REM sleep.

So nose breathing is the body's default at night. When someone breathes through their mouth for much of the night, it usually means something is getting in the way of that default.

Why is the nose the better route during sleep?

A second 2003 study, in the European Respiratory Journal, tested why people favour the nose while asleep. Twelve healthy adults slept in a lab twice, once breathing through the nose and once through the mouth, in random order. Awake, the resistance in their upper airway was about the same either way. Asleep, it was much higher with mouth breathing, with a median of 12.4 units compared with 5.2 through the nose. Breathing pauses and shallow breaths were also far more common when they breathed through the mouth. The authors concluded that nasal breathing gives the airway a mechanical advantage during sleep.

A 2020 computer-modelling study in PLOS One points the same way. It built 3D models of the airways of 14 men with sleep apnea from scans taken while they breathed in different ways. Airflow was smoothest when they breathed through the nose with the mouth closed. With the mouth closed, the tongue rested against the roof of the mouth, while an open mouth let it sit lower. The authors concluded that mouth breathing was the main condition leading to airway collapse in their models. That study was in people with sleep apnea and done while awake, so it doesn't tell you what happens in every sleeper, but it fits with the lab findings above.

What can mouth breathing at night lead to?

Waking up with a dry mouth or a sore throat, snoring, and bad breath in the morning. Saliva protects your mouth, and it dries up when your mouth hangs open for hours.

It may also change the chemistry in your mouth. In a small 2016 study from New Zealand, 10 healthy adults wore a sensor behind their front teeth for several days. Their mouths were a little more acidic during sleep than during the day, with an average pH of 7.0 compared with 7.3. On nights when they wore a nose clip to force mouth breathing, the average dropped to 6.6, and it stayed low for longer. The authors noted that a more acidic mouth has been proposed as a cause of tooth erosion and decay. We cover the dental side in mouth breathing and your teeth, and the morning symptoms in why do I wake up with a dry mouth and does mouth breathing cause bad breath.

Does nasal breathing produce nitric oxide?

Your sinuses make it, and nose breathing delivers it. They release nitric oxide into the nasal airway all the time, and it reaches your lungs mostly when you breathe through your nose. In a small 1996 study, six of eight healthy volunteers had about 10% higher oxygen levels measured through the skin during nasal breathing than during mouth breathing. It's an interesting finding from a tiny study, and nobody has shown that it changes how you sleep. Nitric oxide and nasal breathing goes through what the research does and doesn't show.

Why do people breathe through their mouth at night?

Often the nose feels blocked, from allergies, a cold, a narrow nasal passage or a deviated septum. Sometimes it's just habit. Which one it is for you changes what's worth trying.

Lying down plays a part too. A 2022 meta-analysis of nine studies found that nasal resistance goes up and airflow goes down when you lie flat, and the change was larger in people who snore. A nose that feels fine during the day can feel tight at night for that reason alone. We go through the common causes in why do I breathe through my mouth at night and why is my nose stuffy at night.

How do you stop mouth breathing while sleeping?

Here's the order we'd suggest.

1. Check your nose first. Our two-minute nose test asks you to breathe through your nose with your mouth closed and see how it feels. If that's a struggle, start with the nose rather than the mouth.
2. Clear what you can. Cleveland Clinic suggests keeping pets out of the bedroom, using a humidifier and sleeping with your head and shoulders raised. How to unblock your nose before bed has practical steps.
3. If the front of your nose feels narrow, try a nasal strip. A 2016 meta-analysis noted that nasal dilators have been shown to improve nasal breathing, though they didn't improve sleep apnea measures. A 2007 review of randomised trials found that nasal dilators seemed to reduce snoring. How nasal strips work explains the mechanics.
4. If your nose is clear and your mouth still falls open, try mouth tape. It's a simple way to keep your lips together while you sleep. Start with our first-week guide, and see mouth tape vs. nasal strips if you're deciding between the two or want to combine them.

What are the limits of mouth tape?

The research on tape is still thin. A 2025 systematic review in PLOS One found only 10 studies with 213 patients in total. Results were mixed, many of the studies excluded anyone with a blocked nose, and the reviewers warned of a potentially serious risk for people who tape without checking their nose first. That's why the nose comes first in the steps above.

Leave the tape off when you have a cold or congestion (mouth tape with a cold explains why), don't use it on children, and talk to a doctor before trying it if you snore loudly or might have sleep apnea. Is mouth taping safe? covers the full checklist. For more on this topic, browse our nasal breathing articles.

If you want to try mouth tape and nasal strips together, our pick is the Titan Sleep System, which pairs TitanAir Nasal Strips with Titan Mouth Tape.

* This content is for informational and educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease or health condition. Talk to a qualified healthcare provider about your health.