In short
- The most common cause is something blocking the nose: allergies, a cold, a deviated septum or swollen tissue inside the nose.
- Some people breathe through their nose until deep sleep relaxes the jaw and the mouth falls open.
- Healthy adults with a clear nose breathe almost entirely through it while asleep, so regular mouth breathing at night usually has a cause worth finding.
- Lying down makes the nose measurably narrower, which is why a nose that feels fine by day can feel blocked in bed.
- Fix a blocked nose first. Once nasal breathing is easy, mouth tape is a simple way to keep your lips closed.
Very few people choose to breathe through their mouth at night. It usually happens for one of two reasons: the nose isn't letting enough air through, or the mouth falls open once you're deeply asleep. Both have practical fixes, and which one you have decides what's worth trying first.
Is some mouth breathing at night normal?
A little. In a 2003 study in the Journal of Applied Physiology, researchers measured nose and mouth airflow separately in 10 healthy adults with a clear nose. While they slept, about 4% of the air they breathed in went through the mouth, and that share stayed about the same through every stage of sleep.
So the body's default at night is the nose. If you're waking with a parched mouth most mornings, you've probably drifted well past that 4%, and it's worth working out why.
Reason one: your nose is blocked
Research: moderate (what this means)When air can't get through your nose easily, your body switches to your mouth without asking you. Cleveland Clinic lists these among the common reasons a nose gets blocked:
- allergies, including dust, pet dander and mold in the home
- colds and sinus inflammation
- a deviated septum, where the wall between your nostrils is off-center
- swollen turbinates, structures inside the nose lined with blood vessels that help regulate airflow and filter particles
- nasal polyps, soft noncancerous growths in the lining of the nose
If your nose feels blocked most nights, it's worth seeing a doctor, because some of these causes are easy to treat and others need a specialist. Nasal polyps and breathing and deviated septum symptoms cover two of them in more detail.
Why does it get worse when you lie down?
Lying flat makes your nose a little narrower. A 2022 meta-analysis in The Laryngoscope pooled nine studies with 291 people and found that nasal resistance rises and airflow falls when you lie down. The effect was bigger in people who snore or have sleep apnea, but it showed up in healthy people as well.
Gravity changes how mucus drains too. Cleveland Clinic explains that during the day you swallow mucus as it drains down the back of your throat, but when you lie down it can pool in your sinuses instead. And your nostrils naturally take turns being more congested, which is more noticeable in bed. The nasal cycle explains that part, and why is my nose stuffy at night covers what to do about it.
Reason two: your jaw relaxes
Some people breathe through their nose perfectly well while awake, and even while falling asleep. Then, in deeper sleep, the muscles relax, the jaw drops a little and the lips part. From there it's easier to breathe through the open mouth, and the habit takes over for the rest of the night.
This is the kind of mouth breathing that mouth tape is meant for: a clear nose, and a mouth that just won't stay closed.
How do you know you're doing it?
You're asleep, so you have to go on clues. The most common are waking with a dry mouth or a sore throat, and a partner noticing your mouth hanging open or hearing you snore. Our guides to waking with a dry mouth and a sore throat in the morning go through the other causes of those symptoms, so you can rule them out.
A quick daytime check helps too. Close your mouth and breathe through your nose for two minutes. If that's easy, your nose probably isn't the main problem. If it's a struggle, start there. Our nose test walks you through it.
Why does it matter?
Your nose filters, warms and humidifies the air you breathe, and your sinuses produce nitric oxide that you breathe in through your nose. Breathing through your mouth skips all of that, which is why it so often ends in a dry mouth and a sore throat.
It can also change your mouth itself. In a small 2016 study, healthy adults who wore a nose clip to force mouth breathing during sleep had a more acidic mouth overnight than on normal nights, with an average pH of 6.6 compared with 7.0. The authors noted that a more acidic mouth has been proposed as a cause of tooth erosion and decay.
There's also research on what it does to the airway itself. In a 2003 sleep lab study of 12 healthy adults, resistance in the upper airway during sleep was more than twice as high when they breathed through the mouth than through the nose, even though it was about the same either way while they were awake. A computer-modelling study of people with obstructive sleep apnea found that breathing through the mouth was the main condition that led to the airway collapsing during sleep. Researchers have looked at the nose's role in snoring and sleep apnea for years, and a clear nose is part of the picture.
What you can try
- Deal with the nose first. If allergies or congestion are the issue, talk to a pharmacist or doctor. A nasal strip can make it easier to breathe through a narrow nose at night, and a 2007 review of trials found nasal dilators seemed to reduce snoring.
- Check you can breathe comfortably through your nose with your mouth closed for two minutes.
- If you can, and your mouth still falls open, try mouth tape. Start with our first-week guide.
Cleveland Clinic's tips for a stuffy nose at night are worth adding alongside. They include sleeping with your head and shoulders raised, using a humidifier, showering before bed to rinse off outdoor allergens and keeping pets out of the bedroom.
What if tape doesn't seem to work?
A few common snags have simple fixes. If the tape peels off, lip balm and facial hair are two things to check, and lip balm and mouth tape and mouth tape with a beard cover both. If it feels strange at first, how long it takes to get used to mouth tape sets expectations. Common mouth taping mistakes rounds up the rest.
If you tape and still wake up gasping, or feel you can't get enough air through your nose, take the tape off and go back to the nose. That's a sign the blockage needs attention first.
Is it different for children?
Yes. Mouth breathing in children has its own set of causes and is something to raise with a pediatrician or dentist rather than handle at home. Mouth tape isn't for kids. Mouth breathing in children explains what to look out for.
Check this first. Skip mouth tape and see a doctor if you snore loudly, wake up gasping, have been told you stop breathing in your sleep, or can't breathe comfortably through your nose. More on safety
If you want to try nasal strips, our pick is TitanAir Nasal Strips.
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Common questions
Is it bad to breathe through your mouth while sleeping?
It often leads to a dry mouth, snoring and a sore throat in the morning. In people with sleep apnea, studies suggest mouth breathing makes the airway more prone to collapse.
Is it normal to breathe through your mouth a little at night?
A little, yes. In a 2003 study of healthy adults with a clear nose, about 4% of the air they breathed in during sleep went through the mouth. Breathing through your mouth for much of the night is different and usually has a cause.
Can you train yourself to breathe through your nose at night?
You can make it easier. Clearing a blocked nose helps most. Some people also use mouth tape as a reminder to keep their lips closed, once they've checked they can breathe comfortably through their nose.
Can nasal strips stop mouth breathing?
They can help if a narrow nose is pushing you onto your mouth, since they widen the front of the nose. A 2007 review found nasal dilators seemed to reduce snoring. They won't keep your jaw closed, so people whose mouth falls open even with a clear nose often pair them with mouth tape.
How do I know if I breathe through my mouth at night?
Common clues are waking with a dry mouth or sore throat, snoring, or a partner telling you your mouth hangs open. A quick daytime check is to breathe through your nose with your mouth closed for two minutes and see how it feels.
When should I see a doctor about mouth breathing?
If your nose is blocked most of the time, if you snore loudly, or if anyone has noticed you stop breathing or gasp in your sleep.
Should I mouth tape with a deviated septum?
Only if you can still breathe comfortably through your nose with your mouth closed. The Sleep Foundation lists blockage from a deviated septum among the reasons not to tape, because nasal breathing may not be possible, and Cleveland Clinic says a deviated septum can cause congestion and trouble breathing through one or both nostrils. A two-minute nose test at bedtime is a quick way to check.
Sources
- Why Do I Sometimes Get Congested in One Nostril?
- Why Does My Nose Get Stuffy at Night?
- The effect of nasal and oral breathing on airway collapsibility in patients with obstructive sleep apnea: computational fluid dynamics analyses
- The role of the nose in the pathogenesis of obstructive sleep apnoea and snoring
- High nitric oxide production in human paranasal sinuses
- Partitioning of inhaled ventilation between the nasal and oral routes during sleep in normal subjects
- Effect of nasal or oral breathing route on upper airway resistance during sleep
- The Recumbent Position Affects Nasal Resistance: A Systematic Review and Meta-Analysis
- Intraoral pH and temperature during sleep with and without mouth breathing
- Mouth taping for sleep: does it work?
- Deviated septum
About this article
- Research
- 11 published sources, listed above.
- Evidence
- Moderate. How we rate it
- Last checked
- October 10, 2026
- Funding
- Paid partner of Titan Recovery. Their ads are labeled.
- Found an error?
- Tell us. We log fixes on the corrections page.
* 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.
