Sleep Apnea and Mouth Breathing: Why It Matters for Treatment

Medically reviewed by Allen J. Blaivas, D.O.

Written by Torrey Kim

Posted on September 1, 2026

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Key Takeaways

Many people with sleep apnea find themselves breathing through their mouths at night, which can cause symptoms like dry mouth, bad breath, snoring, and fatigue.

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“I’m not sleeping well because I’m keeping my mouth open all night,” one MySleepApneaTeam member said. “It’s caused a dry mouth and cracked lips.” Another member replied, “I am a mouth breather and have VERY dry mouth issues.”

While sleep apnea may be one reason you’re breathing through your mouth, it’s not the only possible cause of mouth breathing. Keep reading to discover what may be behind this issue. You’ll also learn about treatment options to consider.

How Do You Know if You’re Breathing Through Your Mouth?

Some people may breathe through their mouths and not realize it. This is especially true if you only breathe through your mouth when you’re asleep.

🗳️ How often do you breathe through your mouth at night?

Every night

A few nights a week

Once in a while

Not sure

Other individuals do notice some symptoms that indicate they’re breathing through their mouths. These include:

Dry mouth
Bad breath
Constant fatigue
Drooling as you sleep
Snoring
Hoarseness

These symptoms may occur while you’re awake or just at night. If you wake up with any of these symptoms, it may mean your mouth is open as you sleep.

If you think you might be breathing through your mouth, talk to your healthcare provider. They can perform an exam and ask questions about your medical history.

Your doctor may also perform tests, such as evaluating whether you can breathe when your lips are sealed or holding a mirror under your nose to see if the mirror gets condensation on it.

What Causes Mouth Breathing?

You may be breathing through your mouth instead of your nose for several reasons. Your healthcare provider can help you pinpoint the cause.

Sleep Apnea or Its Treatment

Open-mouth breathing during sleep is common among people with obstructive sleep apnea. Mouth breathing can cause your tongue to move farther back in your throat, partially blocking airflow. This is called airway resistance, and it can make OSA worse.

Even people who are being treated for OSA may experience symptoms like dry mouth due to mouth breathing. The most common sleep apnea treatment is continuous positive airway pressure (CPAP) therapy.

Many CPAP machines have a heated humidifier attached to make the air moist. However, CPAP therapy can lead to dry mouth among people who sleep with their mouths open because it uses dry, cold air. In addition, if your CPAP mask doesn’t fit properly, you may wake up with a dry mouth.

Nasal Congestion

Using a CPAP machine for OSA can lead to nasal congestion, also known as a stuffy nose. When congestion makes it hard to breathe through your nose, you may be more likely to breathe through your mouth.

Allergies

Many people with sleep apnea also have allergic rhinitis (a runny nose due to allergies). One study found that people with OSA are more than twice as likely to have allergic rhinitis than those without OSA.

Allergies may cause structures in your nose (called turbinates) to swell, making it hard to breathe through your nose. This can lead to mouth breathing.

Deviated Septum

Your septum is the thin layer of cartilage and bone that separates the inside of your nose. When the septum leans to one side, it can block airflow and make it hard to breathe through your nose. This is referred to as a deviated septum, and it can lead to mouth breathing.

One study looked at the rate of deviated septums in people with OSA compared to those without it. They found that OSA was more than four times as common in people with deviated septums than in the general population.

Enlarged Tonsils

Enlarged tonsils are the main cause of OSA among children, but swollen tonsils can also affect adults. The link between the two conditions is due to the fact that enlarged tonsils can block your airway when you sleep. This may cause you to open your mouth to try to get more air.

What’s the Harm of Mouth Breathing?

Chronic mouth breathing can lead to complications that go beyond your mouth. That’s why it’s important to treat the cause and improve your comfort and overall health.

Some people who breathe through their mouths have dry lips, decayed teeth, gum disease, cavities, or crowded teeth. They may also experience morning headaches, a sore throat, worse snoring, and digestive problems.

Why Mouth Breathing Matters in People Being Treated for OSA

If you’re breathing through your mouth at night while being treated for OSA, it could affect how well your treatment works. For instance, people who breathe through their mouths may experience more CPAP air leaks. Air leaks reduce CPAP effectiveness.

In addition, those who wake with dry mouths due to mouth breathing may stop using their OSA treatments altogether. But instead of halting OSA treatment, you should try to reduce mouth breathing by using practical solutions that can help.

Consider These Solutions

To reduce mouth breathing while living with OSA, your doctor may suggest certain treatment adjustments. These will be tailored to your specific therapy regimen and overall health. Common solutions include:

Consider a full-face CPAP mask — These usually work better for people who breathe through their mouths at night. Having the right mask can help reduce air leaks.
Add humidification — Some CPAPs come with a humidifier to help reduce dryness. You can adjust the humidity settings to what’s comfortable for you.
Use a chin strap with your CPAP — If you wear a nasal mask with your CPAP, consider getting a chin strap. This can help your mouth stay closed as you sleep.
Consider nasal therapies — Evaluate whether nasal washes, decongestants, nasal strips, allergy medications, or other options may help you breathe through your nose more easily.
Ask your doctor if you need surgery — If enlarged tonsils or turbinates are making nasal breathing harder, surgery may help.

“I just changed my humidity level last night,” one MySleepApneaTeam member said. “It’s been a big help.” Another member said, “I’ve been using a chin strap, and so far so good.”

Other members have said that using mouth tape helped them keep their mouths closed during sleep. But you shouldn’t try this without your doctor’s guidance. In some cases, mouth tape may make it harder to breathe rather than easier, and one study showed mouth tape worsened sleep apnea.

Speak With Your Care Team

If you have OSA and you’re worried about mouth breathing, talk to your sleep specialist. They can help you identify the cause and find solutions so you can sleep better.

If you haven’t been diagnosed with OSA but you noticed you’ve been breathing through your mouth, call your primary care doctor. They’ll perform an exam and determine whether you may need a referral to a sleep specialist, an allergist, or another type of personalized care provider.