CPAP Dry Mouth and Nose: Causes and Fixes

A dry mouth on CPAP does not always show up as leak. ResMed's AirSense 11 guide says to turn up the humidity for a dry nose or mouth, and that a very dry mouth may mean air is escaping through your mouth. A good leak number does not rule that out, because a short stretch of mouth leak can leave a night's typical leak low.

Why CPAP Causes Dryness

Your nose and throat have a natural humidification system. As you breathe normally, the tissues lining your nasal passages warm and moisten incoming air before it reaches your lungs. This works well at normal breathing volumes.

CPAP changes the equation. Your machine pushes a continuous stream of pressurized air through your airway, at a volume and velocity far higher than normal breathing. That pressurized air evaporates the moisture from your nasal passages and throat faster than your body can replenish it.

Then there's the mouth leak problem. If you use a nasal mask and your mouth falls open during sleep, humidified air escapes through your mouth instead of reaching your lungs. It's a vicious cycle: dryness causes congestion, congestion makes you mouth-breathe, and mouth breathing makes the dryness worse.

The result? You wake up with a mouth that feels like sandpaper, a nose that's raw and crusty, or both. Some people develop nosebleeds, sore throats, or nasal congestion that makes CPAP use feel unbearable.

The good news: this is one of the most solvable CPAP problems. Many people can ease dryness with a few simple adjustments.

Turn Up Your Humidifier

If your CPAP has a built-in humidifier (most modern machines do), this is the first thing to try. The humidifier adds moisture to the air before it reaches your mask, counteracting the drying effect of pressurized airflow.

Start by increasing the humidity setting by one level. Going one level at a time and giving each change a few nights makes it easier to tell what helped. Most ResMed AirSense machines have humidity settings that run from Off up to 8. The AirSense 11 user guide (opens in new tab) gives 4 as the default and says to turn up the humidity if you get a dry nose or mouth.

Always use distilled water in your humidifier chamber. Tap water contains minerals that leave white deposits in the chamber and can get into the air you breathe. Distilled water keeps the chamber clean and extends its life. Distilled water is inexpensive and widely available if you don't have a local source.

Refill the chamber every night. Running out of water mid-sleep means you'll wake up dry. Fill it to the max line before bed, every night.

If you're already at maximum humidity and still experiencing dryness, the problem is likely downstream. Keep reading.

Add Heated Tubing

Standard CPAP tubing creates a problem: warm, humid air from the humidifier travels through a cooler tube. The temperature difference causes condensation inside the tube (called "rainout"), and that water collects in the hose instead of reaching your airway. You end up with water gurgling in the tube and dry air at your mask. The worst of both worlds.

Heated tubing solves this by maintaining the air temperature throughout the entire length of the hose. The air stays warm, the humidity stays in the air instead of condensing on the tube walls, and you get the full benefit of your humidifier setting.

If you're using a ResMed AirSense 10 or 11, a ClimateLineAir heated tube works with the machine's climate control system, automatically adjusting tube temperature based on the room conditions and your humidity setting. The two machines use different tubes that are not interchangeable. The AirSense 10 uses the original ClimateLineAir, and the AirSense 11 uses the ClimateLineAir 11. Make sure the tube you buy matches your machine.

For many people, combining a higher humidity setting with heated tubing makes a big difference. If you're still experiencing issues, the cause is likely mouth leak or environmental factors.

Use a Nasal Spray or Gel Before Bed

A saline nasal spray before putting on your mask adds a protective layer of moisture to your nasal passages. It's a simple step that makes a noticeable difference, especially during winter when indoor air is already dry.

Saline spray (not a medicated decongestant spray) is a plain salt water spray for your nose. Check the label to be sure it has no decongestant in it, and ask a pharmacist if you are not sure. A quick spray in each nostril 5–10 minutes before bed moisturizes the nasal lining and helps your passages handle the airflow. Saline nasal sprays designed for CPAP users are widely available.

Nasal gels are a thicker option that lasts longer through the night. Apply a small amount just inside each nostril before bed. These are especially helpful if you live in a dry climate or run your heating system all winter.

A bedroom humidifier can also help by raising the ambient moisture level in your room. This reduces how hard your CPAP humidifier has to work and helps your nasal passages stay comfortable. This is a complementary fix, not a replacement for your CPAP's built-in humidifier.

Try a Chin Strap (for Mouth Leakers)

If you use a nasal mask or nasal pillows and you wake up with a dry mouth, you may be mouth-breathing during sleep. Your humidifier is working fine, but the moist air is escaping through your open mouth before it can do any good.

A CPAP chin strap wraps around your head and under your jaw, gently holding your mouth closed during sleep. It keeps the humidified air circulating through your nasal passages where it belongs.

Tips for chin strap success:

• Fit it snugly but not tightly. It should keep your jaw from dropping open, not clamp your mouth shut. You should be able to swallow comfortably.
• Give it a few nights. It feels strange at first.
• Check your leak data. If your leak drops after adding a chin strap, that points to mouth leak as part of the cause. If it does not change, read the section below on dry mouth when your leak looks good, because a low leak number does not prove your mouth stayed closed.

Some people find chin straps uncomfortable or ineffective, especially if nasal congestion forces them to mouth-breathe. If that's the case, a full face mask may be a better solution.

Consider a Full Face Mask

If you can't stop mouth breathing (due to nasal congestion, jaw structure, or habit), a full face mask can help. It covers both your nose and mouth, so even if your mouth opens during sleep, the humidified air stays within the sealed mask system.

Full face masks have gotten significantly more comfortable in recent years. Newer full face designs are often lighter and less bulky than older ones (masks for mouth breathers). The tradeoff is a larger sealing surface, which means more potential for leak, but for chronic mouth breathers, the improvement in comfort and humidity delivery usually outweighs that concern.

Talk to your equipment provider about trying a full face mask. Many offer 30-day trial periods.

If mouth breathing is the root of your dryness, our guide to the best CPAP masks for mouth breathers compares the full face and hybrid options that keep the humidified air sealed in when your mouth falls open at night.

Dry Mouth When Your Leak and Score Look Good

A good mask seal score or a low leak number says the seal held for most of the night. It does not say your mouth stayed closed all night. ResMed explains that myAir looks at how your leak values are spread across the whole night, "so even though your overall seal can be 'good', there might have been short periods of high mask leak." It adds that short periods of high leak can happen when you roll over in bed or open your mouth while using a nasal or pillows mask.

Why a good number can sit beside a dry mouth

The typical leak is the middle of the night. CPAP Clarity gives a night's typical leak as the median, the level the leak stays under for half the night. A stretch of mouth leak that fills less than half the night can leave that middle value low. That is how a median works, not a ResMed statement.

ResMed's Good line leaves room too. For the AirSense 10's Sleep Report screen, ResMed's clinical guide calls the Mask Seal "Good" if the 70th percentile leak is less than 24 L/min. In our reading, the leakiest 30% of the night is not part of that test, so a night can read Good with a stretch of high leak in it. ResMed uses a different line in its AirMini app, where a good mask seal means less than 24 L/min of leak at the 95th percentile. In myAir, ResMed says your score reduces as your mask leak increases; it does not publish the leak line myAir scores against.

An open mouth on a nasal mask lets the humidity out. A 2000 study in the journal Chest measured the air inside the mask of people on long-term nasal CPAP who complained of nasal discomfort. In its daytime test of 17 of them, the relative humidity in the mask fell to 39% with a simulated mouth leak, against 80% breathing without CPAP. A heated humidifier raised it to 63% with a simulated mouth leak, short of the 80%, while a face mask kept it at 84%. The authors concluded that heated humidification can significantly reduce the dryness, even during mouth leaks, and that a face mask can prevent it entirely. So turning up the humidity may help, and may still fall short if your mouth is open on a nasal mask. A smaller 1996 study in six healthy volunteers found that 10 minutes of deliberate mouth leak on nasal CPAP sharply raised the resistance to airflow through the nose, and that a heated water bath humidifier greatly reduced the rise.

What you feel and what the machine reports can differ. In the InterfaceVent study of 1,484 people on long-term CPAP, published in Respiratory Research in 2021, 75.4% of those who answered reported leaks, and those reports had no correlation with the leak their CPAP recorded. The same study found dry mouth was associated with using CPAP under 4 hours a day (the study's cut-off for non-adherence). So a low leak number on a morning you woke up parched does not settle it.

When your leak data cannot see it

• A full face mask. If your mouth opens inside a full face mask, the air stays inside the mask, so an open mouth alone gives the machine nothing to count (a jaw that drops far enough to shift the cushion can still break the seal). That is our reading of how the mask works, not a maker's statement. In the 2000 study above, a face mask held the humidity in the mask with the mouth open. If you are still dry on a full face mask with a low leak, look at the humidity settings, the room, and causes outside CPAP.
• A chin strap that only partly closes your mouth. A 2004 study in Sleep Medicine of 15 people with mouth leak who complained of mouth dryness found a chin strap cut mouth leak from 42.9% to 23.8% of sleep time on average, and the authors still called the remaining figures unacceptably high. The same study found snoring time went up with the strap, from 6.7% to 24.0% of sleep time. A strap can reduce mouth leak without stopping it. None of the maker guides cited here mention mouth tape, so talk to your provider before adding tape or a strap.
• A dry mouth with a cause outside CPAP. The National Institute of Dental and Craniofacial Research says hundreds of medicines can cause the salivary glands to make less saliva, naming medicines for high blood pressure, depression and bladder-control issues, and that some diseases can cause dry mouth too. It advises seeing your dentist or doctor to find out why your mouth is dry. Do not stop or change a medicine on your own; ask your doctor or pharmacist.

How to check your own nights

On CPAP Clarity, here is where to look after you import your SD card.

• The sentences under the night's count. The leak sentence gives the night's typical leak ("Mask leak was ... L/min"). On a summary-only machine the sentence gives the 95th percentile instead, and on a machine that records only an average, the sentence says so and the night is not graded against any line.
• "What your data means." When a night's typical leak is under 24 L/min but its leakiest 5% (the 95th percentile) runs above 36 L/min, this list says your seal held for most of the night but leak ran high for part of it. When the typical leak is under 15 L/min but the highest reading tops 100 L/min, it notes brief seal breaks. Reading your typical leak against 24 is this site's use of ResMed's line, and the 15, 36 and 100 are this site's own.
• "Every chart and number." Open this drawer at the bottom of the night. Under "The night's numbers", the Leak Rate row lists Min, Median, P95, P99.5 and Max. A low Median beside a much higher P95 or Max is the shape of short leak stretches. Under "Detailed charts", the Leak Rate row sits on the same clock as your events, so you can see when they happened. Our guide to P95 on CPAP explains the percentile.
• History. On ResMed machines, "When in the night your leak is highest" says whether your leakiest minutes keep landing in the same part of the night. "Compare Periods" lets you mark the date you changed something, such as a chin strap or a humidity level, and shows Before and After side by side.

Keep a note of the mornings you wake up dry, then line them up with those nights. A dry morning after a night with a high P95 points toward short leak stretches. A dry morning after a night that is low all the way through points toward the causes in the list above. Neither is a diagnosis, and both are worth bringing to your provider. The leak pattern finder and our mask leak guide go further into reading the leak itself, and our myAir score guide explains what the score counts.

What the makers suggest

ResMed's AirSense 11 guide lists the answer for "My mouth is very dry and uncomfortable" as "Air may be escaping through your mouth," with a chin strap to keep your mouth closed or a full face mask. For a dry nose or mouth it says to turn up the humidity. Its Climate Control Auto setting adjusts the humidifier to keep a constant 85% relative humidity, and it works only with both the ClimateLineAir 11 tube and the HumidAir 11 tub attached. Fisher & Paykel says to check that your mask fits well with no excessive leaks, because a leaky mask can also make your mouth and throat feel dry, and to drink water through the day. Our humidity settings guide covers the levels. Pressure is your provider's decision, so leave it alone and raise the dryness with them.

When to See Your Doctor

Most CPAP dryness is fixable with the adjustments above. But see your doctor or sleep specialist if:

• You have persistent nosebleeds that don't improve with humidification and saline spray
• Your nasal congestion is chronic, making it impossible to breathe through your nose even during the day
• You suspect your pressure needs adjusting. Your doctor can review your data and your settings.
• Your mouth stays painfully dry on nights your leak reads low. Bring a few of those nights and a list of the medicines you take, since dry mouth has causes outside CPAP.
• You develop sinus pain or infections. Repeated sinus infections while using CPAP could indicate a problem that needs medical attention.
• Dryness is causing you to skip nights. Inconsistent use is a bigger problem than dryness itself. Your doctor would rather help you solve the comfort issue than have you stop therapy.

Frequently Asked Questions

Why does my CPAP give me dry mouth?

Your machine pushes a continuous stream of pressurized air through your airway at a volume and velocity far higher than normal breathing, which evaporates moisture from your nasal passages and throat faster than your body can replenish it. If you use a nasal mask and your mouth falls open during sleep, humidified air escapes through your mouth instead of reaching your lungs.

Why do I wake up with a dry nose using CPAP?

Pressurized airflow dries out the tissues lining your nasal passages faster than they can rebuild their natural moisture. This can leave your nose raw and crusty, and some people develop nosebleeds or nasal congestion. Indoor air is often already dry in winter, which makes the effect worse.

What humidifier setting stops CPAP dry mouth?

Start by increasing your humidity setting by one level. Going one level at a time and giving each change a few nights makes it easier to tell what helped. Most ResMed AirSense machines have humidity settings that run from Off up to 8, and the AirSense 11 guide gives 4 as the default and says to turn up the humidity if you get a dry nose or mouth. Always use distilled water and refill the chamber to the max line every night so you do not run out mid-sleep.

Does a chin strap help with CPAP dry mouth?

If you use a nasal mask or nasal pillows and wake up with a dry mouth, you may be mouth-breathing, and a chin strap gently holds your mouth closed so the humidified air stays in your nasal passages. Fit it snugly but not tightly (you should be able to swallow comfortably) and give it a few nights to adjust. Some people find chin straps uncomfortable or ineffective, especially when nasal congestion forces them to mouth-breathe.

Should mouth breathers use a full face mask to fix dryness?

If you cannot stop mouth breathing due to nasal congestion, jaw structure, or habit, a full face mask covers both your nose and mouth so the humidified air stays within the sealed mask system even if your mouth opens. Modern designs are lighter and less bulky than older models. The tradeoff is a larger sealing surface and more potential for leak, but for chronic mouth breathers the improvement usually outweighs that concern, and many providers offer 30-day trial periods.

Can I use nasal spray or gel with my CPAP?

Yes. A plain saline spray (not a medicated decongestant) moisturizes the nasal lining, and a quick spray in each nostril 5 to 10 minutes before bed is enough. Check the label for a decongestant, and ask a pharmacist if you are not sure. Nasal gels are a thicker option that lasts longer through the night, applied just inside each nostril before bed. Both are especially helpful in a dry climate or when you run your heating system all winter.

Why is my mouth dry when my leak and score look good?

A good seal score or a low typical leak means the seal held for most of the night, not that your mouth stayed closed. ResMed says your seal can read 'good' overall even when there were short periods of high leak, and the AirSense 10's Sleep Report calls the seal Good when the 70th percentile leak is under 24 L/min. On a full face mask an open mouth alone is not counted as leak. Check the P95 and Max beside the Median for the night.

What to Try First

CPAP dryness is uncomfortable, but it's not something you have to live with. Start with your humidifier settings and distilled water. Add heated tubing if condensation is stealing your humidity. Use saline spray for extra nasal protection. And if mouth leak is the culprit, a chin strap or full face mask can help keep the moist air where it needs to be.

Your SD card data can tell you exactly what's happening. Analyze your CPAP data free with CPAP Clarity →

Primary Sources

• ResMed. AirSense 11 user guide. Drying of the nose, mouth or throat among possible side effects, Climate Control Auto keeping 85% relative humidity with the ClimateLineAir 11 and HumidAir 11 attached, "If you are getting a dry nose or mouth, turn up the humidity", and the troubleshooting entry "My mouth is very dry and uncomfortable". ResMed AirSense 11 user guide (PDF) (opens in new tab)
• ResMed. AirSense 10 Clinical Guide. Sleep Report Mask Seal "Good" if the 70th percentile leak is less than 24 L/min. ResMed AirSense 10 Clinical Guide (PDF) (opens in new tab)
• ResMed. What does "good mask seal" mean? The AirMini app's line at the 95th percentile. ResMed good mask seal FAQ (opens in new tab)
• ResMed. Why did I receive an email saying my mask is leaking? myAir looks at how leak values are spread across the whole night. ResMed myAir leak email FAQ (opens in new tab)
• ResMed. When do I experience short periods of high mask leak? ResMed short leak periods FAQ (opens in new tab)
• ResMed. How is mask seal calculated? myAir mask seal points and mouth leak with a nasal or nasal pillows mask. ResMed mask seal FAQ (opens in new tab)
• Fisher & Paykel Healthcare. How to prevent dry mouth when using CPAP? F&P dry mouth guide (opens in new tab)
• Martins De Araújo MT, Vieira SB, Vasquez EC, Fleury B. Heated humidification or face mask to prevent upper airway dryness during continuous positive airway pressure therapy. Chest. 2000 Jan;117(1):142-7. PubMed 10631212 (opens in new tab)
• Richards GN, Cistulli PA, Ungar RG, Berthon-Jones M, Sullivan CE. Mouth leak with nasal continuous positive airway pressure increases nasal airway resistance. Am J Respir Crit Care Med. 1996 Jul;154(1):182-6. PubMed 8680678 (opens in new tab)
• Rotty MC, Suehs CM, Mallet JP, et al. Mask side-effects in long-term CPAP-patients impact adherence and sleepiness: the InterfaceVent real-life study. Respir Res. 2021 Jan 15;22(1):17. PubMed 33451313 (opens in new tab)
• Bachour A, Hurmerinta K, Maasilta P. Mouth closing device (chinstrap) reduces mouth leak during nasal CPAP. Sleep Med. 2004 May;5(3):261-7. PubMed 15165532 (opens in new tab)
• National Institute of Dental and Craniofacial Research. Dry Mouth. NIDCR dry mouth page (opens in new tab)