9 effects of mouth breathing at night

Breathing through your mouth at night dries out your mouth and throat, which can leave you with a sore throat, bad breath and drool on the pillow by morning. It's also linked to snoring, a more acidic mouth and an upper airway that works harder than it does with nasal breathing. Cleveland Clinic says it isn't a serious health issue for adults, and most fixes start with your nose.

For context, healthy adults with a clear nose breathe only about 4% of their air through the mouth during sleep, according to a 2003 study. When that share climbs, here's what tends to happen.

What effects of mouth breathing do you feel in the morning?

Your mouth dries out

The NHS lists breathing through your mouth at night as a main cause of dry mouth, whether from a blocked nose or simply sleeping with your mouth open. Dry mouth is more than uncomfortable. The National Institute of Dental and Craniofacial Research says saliva washes food away from teeth and gums and contains minerals that help keep teeth strong, so a mouth that stays dry raises the risk of tooth decay. The NHS suggests keeping water by your bed, brushing twice a day and using an alcohol-free mouthwash if your mouth is often dry. Dry mouth at night remedies covers what helps.

Your throat feels sore and your voice sounds rough

Cleveland Clinic explains that breathing through your nose keeps moisture in your mouth and throat, and that sleeping with your mouth open lets saliva dry out instead of keeping your throat lubricated. Mouth breathing is one of the reasons it gives for waking with a sore throat, and hoarseness is on its list of common mouth breathing symptoms.

Your breath is worse

Morning breath happens when your mouth dries out overnight and bacteria multiply, Cleveland Clinic says. Saliva normally washes away food particles and bacteria, but it slows down during sleep. Cleveland Clinic names congestion and mouth breathing among the things that make the problem worse, and bad breath is one of its common mouth breathing symptoms. Does mouth breathing cause bad breath? goes into more detail.

You find drool on your pillow

Drool on your pillow sounds like the opposite of dry mouth, but it comes from the same open mouth. Cleveland Clinic lists drooling when asleep as a common symptom, and explains that when you sleep with your mouth open, saliva either dries out or escapes as drool.

Your lips crack

The NIDCR lists cracked lips among the symptoms of dry mouth, along with a dry feeling in the throat. If your lips are chapped every morning even when the weather is mild, a night of air moving across them is a reasonable suspect.

What does mouth breathing do during the night?

You're more likely to snore

The Sleep Foundation explains that snoring often occurs when someone breathes through the mouth, which can make the soft tissues in the throat vibrate. Cleveland Clinic lists snoring among the common symptoms of mouth breathing. Not every snorer is a mouth breather, but if a partner says your mouth hangs open while you snore, the two are probably connected. Position matters as well: the Sleep Foundation says decades of research show people snore less on their side than on their back.

Your airway works harder

In a 2003 sleep lab study of 12 healthy adults, upper airway resistance during sleep was a median of 12.4 units with mouth breathing compared with 5.2 with nasal breathing. When awake, the two routes were about equal. In other words, breathing through the mouth while asleep made the airway more than twice as hard to breathe through, which the authors suggested is why the body defaults to the nose. The same study also counted far more obstructive breathing pauses during mouth breathing. That's a finding about breathing route in a sleep lab, not evidence that mouth tape treats sleep apnea, and anyone with signs of sleep apnea needs a proper diagnosis.

You may wake up tired

Cleveland Clinic lists feeling tired all the time as a common symptom of mouth breathing and says it can affect your sleep. Tiredness has many possible causes, though. Heavy daytime sleepiness alongside loud snoring, choking or gasping is a warning sign of sleep apnea, according to the Sleep Foundation, and that needs a doctor rather than a home fix. The Sleep Foundation warns that trying mouth tape instead of seeing a doctor could delay important treatment.

How does mouth breathing affect your teeth?

Your mouth becomes more acidic

In a small 2016 study, 10 healthy adults wore a nose clip on some nights to force mouth breathing. The average pH in their mouths during normal sleep was 7.0, and with mouth breathing it fell to 6.6, dropping further and for longer over the night. The authors noted that lower pH has been proposed as a cause of tooth erosion and decay. In children and teens, a 2026 systematic review found mouth breathing was associated with more gum bleeding and plaque. How mouth breathing affects your teeth has more.

A note on children: Cleveland Clinic says mouth breathing in kids can affect growth, behavior and face shape. A child who breathes through the mouth should see a pediatrician, and tape isn't for children. Mouth breathing in children explains what to look for.

Why does mouth breathing happen, and what helps?

Most people breathe through the mouth because air can't get through the nose easily, Cleveland Clinic says, from congestion, allergies, a deviated septum, enlarged turbinates or nasal polyps, and a doctor will treat whatever is keeping air out of your nose, for example with antihistamines or steroid sprays for allergies, or surgery such as septoplasty or turbinate reduction for structural problems. So start with your nose. A doctor may use a lip seal test, which Cleveland Clinic describes as checking whether you can breathe with your mouth closed. Our two-minute nose test is a quick version you can do at home. If your nose feels narrow, a nasal strip can help. A 2016 meta-analysis noted that nasal dilators have been shown to improve nasal breathing, though they didn't change sleep apnea measures.

If your nose is clear and your mouth still falls open, mouth tape is a simple, comfortable way to keep your lips together so air takes the route your body prefers. The Sleep Foundation calls it a gentle reminder that promotes nasal breathing, and recommends testing it during the day first and using a porous tape made for skin. The research is still small, and a 2025 review warned of serious risk for anyone who tapes with a blocked nose. Leave it off when you're congested, and see a doctor first if you might have sleep apnea. Our first-week guide helps you ease in.

Our pick: Titan Bamboo Silk Mouth Tape (paid partner)

The tape we recommend is Titan Bamboo Silk Mouth Tape. Titan says it's a bamboo silk strip rather than kinesiology tape, with a SilkSeal adhesive made to grip through stubble and full beards without tugging hair or leaving residue, and no printed ink on the side that touches your skin. It's one oval size, 76 mm by 38 mm, worn horizontally across the lips. Titan suggests 20 to 30 minutes of daytime practice before your first night, says every batch is third-party tested and certified PFAS-free, and offers a 30-night guarantee.

For more, browse our nasal breathing articles.

Read next

• 9 signs you breathe through your mouth at night
• 8 benefits of breathing through your nose
• Why do I breathe through my mouth at night?

* 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.