CPAP Dry Mouth and Stuffy Nose: Causes and How to Fix Them

A dry mouth is one of the most common complaints in the first weeks of CPAP. It's also one of the easiest to fix once you know the cause. CPAP dry mouth nearly always comes down to one of two things: the air isn't humid enough, or air is escaping through your mouth while you sleep. A blocked or stuffy nose is closely linked, because a congested nose pushes you to breathe through your mouth. This guide explains what's happening, how to adjust your humidifier settings, and which mask and accessory changes help. It also covers when to talk to your GP or sleep specialist.

Why CPAP causes a dry mouth

Your nose normally warms and moistens every breath. CPAP delivers a steady stream of pressurised air, and that extra airflow can dry the lining of your nose, mouth and throat faster than your body can keep up. A heated humidifier replaces that lost moisture.

The bigger cause is a mouth leak. If you use a nasal or nasal pillow mask and your mouth falls open during sleep, the pressurised air takes the easiest way out. It flows in through your nose and straight out through your mouth, all night long. That constant one-way stream dries your mouth and throat much faster than normal breathing, and the humidifier can't keep up with it. That's why people with a mouth leak often wake with a mouth that feels parched even when their humidifier is on.

A mouth leak isn't just uncomfortable. Air escaping through the mouth can lower the pressure reaching your airway, so your therapy may be less effective than your machine's settings suggest.

Match your symptom to the likely cause

Step 1: Get your humidifier settings right

If you only change one thing, make it humidity. Most modern machines, including the ResMed AirSense 10 and AirSense 11, have an integrated heated humidifier. It's worth checking that it's switched on, has water in the tub, and is set high enough.

What the settings mean (ResMed AirSense 11)

• Climate Control Auto is the default. It sets the heated tube to 27°C and adjusts the humidifier to hold the air at about 85% relative humidity. For most people this is the best place to start, and it's designed to prevent rainout.
• Climate Control Manual lets you set the humidity level and tube temperature yourself. You get more control, but ResMed notes that rainout protection isn't guaranteed.
• Humidity level runs from Off, then 1 (lowest) to 8 (highest). If you wake with a dry mouth or nose, go up one step at a time and give each change a night or two.
• Tube temperature can be set from 16°C to 30°C, or turned off. A warmer tube keeps the moisture in the air instead of letting it condense on the way to your mask.

Other machines, including Philips DreamStation and Fisher & Paykel models, use different scales, so check your user guide for the equivalent settings.

More humidity, but watch for rainout

Raising humidity is the right fix for dryness. The catch is rainout: warm, moist air cools as it travels down the tube, and the moisture condenses into water droplets. You'll notice gurgling, droplets in the mask, or a wet face. It's most common in winter or in a cool bedroom. If it happens, raise the tube temperature first. Only lower the humidity if that doesn't work. Turning humidity straight back down usually brings the dry mouth back.

A heated tube makes the biggest difference here. It keeps the air warm all the way to your mask, so you can run higher humidity without condensation. For the AirSense 11 that's the ClimateLineAir 11 heated tube. For the AirSense 10 it's the ClimateLineAir heated tube. You'll find other options in our CPAP tubes range.

Look after the tub

Fill the tub to the maximum line before bed. A tub that runs dry partway through the night gives you dry air in the early hours. Use the water your tub is designed for. The AirSense 11 guide calls for distilled water in the standard tub and allows drinking-quality water in the cleanable tub. Replace the tub on schedule, because a cracked or cloudy one won't heat evenly. Replacement tubs and seals are in our humidifier chambers and parts range.

Step 2: Stop air escaping through your mouth

If you still wake with a dry mouth after raising the humidity, a mouth leak is the most likely reason. You may not know you're doing it. Common signs:

• your mouth is dry on waking but your nose feels fine
• a partner hears air rushing or sees your mouth open
• your machine or app reports high leak even though the mask feels well fitted. ResMed's myAir app, for example, shows a mask seal score

Add a chin strap

A CPAP chin strap is a soft band that cups the chin and runs over the top of the head, gently supporting your jaw so your mouth stays closed. It's the simplest fix for mouth leak with a nasal or nasal pillow mask, and many people prefer it to changing masks. A chin strap supports the jaw but doesn't seal the lips, so it won't help everyone. If you still get a dry mouth after a week or two, consider the next option.

Switch to a full face mask

A full face mask covers both your nose and mouth, so air can't escape through your mouth. It's often the most reliable fix for habitual mouth breathers, and for anyone whose nose blocks up regularly with allergies or colds. The trade-off is a larger mask with more surface to seal, so fit matters more. If you're not sure which style suits you, our guide to the different types of CPAP masks explains the options.

What about mouth tape?

Some CPAP users tape their lips closed at night. Mouth tape isn't designed as part of CPAP therapy, and it isn't suitable for everyone. It can be unsafe if your nose blocks up during the night, or if you feel nauseous or might vomit. If you're considering it, talk to your GP or sleep specialist first. Never use it with a nose that's often congested.

Step 3: Check your mask fit and cushion

A leak around the cushion lets humidified air escape before you breathe it in, and the extra airflow dries your nose and mouth. On the AirSense 11, the Mask Fit function runs the air at pressure so you can check for leaks. ResMed treats a leak under 24 L/min as a good seal. Above that, the mask needs adjusting.

• Fit the mask while lying in your usual sleeping position, not sitting up.
• Don't overtighten the headgear. Pulling it tight often creases the cushion and causes more leaks.
• Check the size. A cushion that's too large or too small rarely seals well.
• Replace worn parts. Silicone cushions lose their seal over time, and ResMed recommends replacing most cushions every six months, or sooner if they're torn, discoloured or hard to clean. Memory foam cushions need replacing monthly.

Replacement parts for most ResMed, Fisher & Paykel and Philips masks are in our cushions and seals range.

Step 4: Look after a stuffy or blocked nose

Nasal congestion and dry mouth feed each other. A blocked nose forces you to breathe through your mouth, and mouth breathing dries you out. Some people also find their nose runs or blocks up in the first weeks of CPAP as the nasal lining reacts to the airflow.

• Increase humidity first. Heated humidification often settles a CPAP-related stuffy nose within a night or two.
• Try a saline nasal spray before bed to moisten the nasal passages. Your pharmacist can recommend one.
• Treat allergies or hay fever. Ask your pharmacist or GP about suitable options, especially before starting any medicated nasal spray.
• Change your mask if your nose blocks often. Nasal pillow masks and nasal masks depend on a clear nose. If congestion is a regular problem, a full face mask means your therapy keeps working on the nights your nose doesn't.

Other things that can make dryness worse

• Your bedroom air. Reverse-cycle air conditioning and heaters dry the air, and a cold room makes rainout more likely. That can tempt you to lower the humidity when you should be raising the tube temperature.
• Medications. Many common medicines list dry mouth as a side effect, including some antihistamines, antidepressants and blood pressure tablets. Don't stop a medicine yourself. Ask your pharmacist or GP whether it could be contributing.
• Alcohol before bed. Alcohol relaxes the jaw and throat muscles, which makes mouth breathing more likely.
• Your pressure. Higher pressures move more air and can increase dryness and leaks. Never change a prescribed pressure yourself. If you think it's a factor, raise it with your sleep physician.

When to see your GP or sleep specialist

Most CPAP dryness settles with the steps above. See your GP or sleep specialist if:

• your nose is blocked most nights, or you've always struggled to breathe through one side. A deviated septum, polyps or chronic rhinitis may need treatment of their own
• you get nosebleeds, sinus pain or a sore throat that doesn't settle
• you still have a dry mouth after trying humidity, a chin strap and a full face mask
• you're waking unrefreshed, or your machine shows a rising AHI or high leak, which suggests your therapy isn't working as well as it should

Frequently asked questions

Should CPAP humidity be turned up or down for a dry mouth?

Up. More humidity is the right response to a dry mouth, nose or throat. Increase it one step at a time. If you then get water in the tube or mask (rainout), raise the tube temperature or use a heated tube rather than turning the humidity back down.

Is a dry mouth with CPAP normal?

It's common, particularly in the first few weeks, but you don't need to put up with it. It usually means the humidity is too low or air is escaping through your mouth, and both can be fixed.

Will a chin strap work with a nasal pillow mask?

Yes. A chin strap can be worn with nasal and nasal pillow masks, and that's the combination it's designed for. It won't help with a full face mask, because the mask already covers your mouth.

Can CPAP dry mouth affect my teeth?

Saliva helps protect teeth from decay, so a mouth that's dry night after night may raise the risk of dental problems. Fixing the cause is the best protection. Mention your CPAP use to your dentist so they can keep an eye on it.

Does a dry mouth mean my CPAP isn't working?

Not necessarily, but it's worth checking. If the dryness comes from a mouth leak, some of your pressure is escaping. Look at your machine's leak and AHI readings, or your app's mask seal score. If they're poor, fix the leak before assuming your therapy is fine.

Get your therapy comfortable again

A dry mouth or stuffy nose shouldn't be the reason you give up on CPAP. Start with humidity, then deal with any mouth leak, then check your mask. Most people are comfortable again within a week. Browse our chin straps, full face masks and heated tubes, or contact our team if you'd like help working out what's causing your dryness.