CPAP Side Effects: Dry Mouth, Bloating and a Blocked Nose
CPAP Side Effects: Dry Mouth, Bloating and a Blocked Nose
Almost every CPAP side effect is a signal, not a verdict. Dry mouth means air is escaping somewhere. Bloating means you're swallowing it. Here's what each one is telling you — and what actually fixes it.
Jump to your symptom.
Nearly all of them come from one of three things.
CPAP side effects feel random and personal, which is why so many people conclude the therapy simply doesn't agree with them. In practice almost all of them trace back to one of three causes: air going somewhere it shouldn't, air that's too dry, or a mask that doesn't fit the way it did when it was new.
That matters because all three are adjustable. Dry mouth isn't a verdict on whether you can tolerate CPAP — it's a signal that air is escaping past your lips or around the cushion. Bloating isn't your body rejecting therapy — it's air going down the oesophagus instead of the airway. A blocked nose each morning isn't an allergy you've suddenly developed — it's usually a humidity setting.
Give it a fortnight before you judge anything
Some mild effects genuinely do settle. Pressurised air through the nose is an unfamiliar sensation, and the first two weeks involve a certain amount of adaptation — a slightly dry throat, odd dreams, waking when you turn over. If something is mild and new, it's reasonable to give it ten to fourteen nights before changing anything.
But "give it time" is bad advice for anything that is painful, getting worse, or stopping you sleeping. Those need a change, not patience, and the rest of this guide covers what that change usually is.
Change one thing at a time
The most common mistake is fixing everything at once — new mask, new humidity setting, chin strap, different sleeping position, all in one night. When things improve you've no idea which change did it, and when they don't you've no idea what to undo. Make one adjustment, give it three or four nights, then decide.
One rule throughout: never change your prescribed pressure settings yourself. Several of the fixes below involve pressure, and every one of those is a conversation with your sleep clinic, not something to adjust on the machine.
Dry mouth and a sore throat.
The most reported CPAP side effect by a wide margin — and the one most often misdiagnosed as "I just need more humidity". Humidity helps the symptom. It rarely fixes the cause.
Work through it in this order
1. Fit a new cushion. If yours is more than a month old, replace it before changing anything else. Hardened silicone is the single most common cause of new leaks, and a leaking mask dries your mouth no matter how much humidity you add.
2. Turn the humidity up one step. Not to maximum — one step, for three or four nights. Over-humidifying creates condensation in the hose, which brings its own problem.
3. Work out whether your mouth is opening. If dryness persists with a good seal and decent humidity, mouth breathing is the likely culprit. A chin strap is the cheapest test: if a few nights with one noticeably improves things, you've found it.
4. Consider a full face mask. If you're a confirmed mouth breather, or you get congested regularly, a full face mask covering nose and mouth sidesteps the problem rather than managing it. Many people resist this because full face masks look bulkier, but a well-fitted one is far more comfortable than months of waking up parched.
What won't fix it
Drinking more water before bed treats the symptom for about an hour and wakes you up for the bathroom. Sucking sweets or using a strong mouthwash can make dryness worse. And simply enduring it isn't harmless — chronic overnight dry mouth raises the risk of dental decay and gum problems, so it's worth solving properly rather than tolerating.
Bloating, burping and trapped air.
Swallowing air during CPAP therapy is called aerophagia, and it's unpleasant in a way that surprises people: a tight, distended stomach in the morning, excessive burping, wind, and sometimes genuine abdominal pain. It happens when pressurised air travels down the oesophagus into the stomach instead of into the airway.
It usually means the pressure arriving is higher than what your airway comfortably accepts at that moment — so some of it takes the other route. That's why it's often worst in the early part of the night, before you're deeply asleep, and why it's more common in people on higher pressures.
What helps, in rough order of how easy it is to try
Change your sleeping position. Sleeping on your left side, or raising the head of the bed slightly, both reduce how readily air enters the stomach. Elevating the whole upper body with a wedge works better than stacking pillows, which bends the neck and can make airway obstruction worse.
Check for a leak first. This sounds counterintuitive, but a leaking mask makes a machine work harder to maintain pressure, and the resulting bursts can increase swallowing. A fresh cushion and a proper refit is worth doing before anything else.
Ask your clinic about EPR or pressure relief. Expiratory Pressure Relief lowers the pressure as you breathe out, which many people find reduces aerophagia considerably. On ResMed machines this is an adjustable setting — but it's one your clinician sets, not you.
Ask about your ramp settings. A longer, gentler ramp means you're not receiving full therapeutic pressure while still awake and swallowing normally. Again, a clinic adjustment.
Ask whether your pressure is higher than it needs to be. If aerophagia is persistent and nothing else helps, it's a legitimate reason to request a therapy review. Pressures are sometimes set higher than currently necessary, particularly if your weight or circumstances have changed since the original titration.
Two things to avoid: don't eat a large meal or drink fizzy drinks close to bedtime, and don't reduce your own pressure to make the bloating stop. Lowering pressure below what you need quietly undoes your therapy while leaving your usage hours looking perfect.
A blocked, runny or streaming nose.
Confusingly, both too little and too much humidity cause nasal problems — and they need opposite fixes. Working out which one you have is most of the job.
Rhinitis that isn't about humidity at all
Some people develop genuine nasal inflammation in response to the constant airflow — a persistently blocked or runny nose that doesn't respond to humidity changes either way. A saline rinse before bed helps some people. If it continues, it's worth discussing with your GP or sleep clinic rather than self-treating, since a nasal steroid spray or an underlying allergy may be involved, and those need proper assessment.
When you've got a cold
Short-term congestion from a cold or hay fever makes a nasal mask genuinely difficult to use, and a lot of people abandon therapy for the week. A better plan is to have a full face mask available as a backup, so blocked nights don't become missed nights. If you only own one mask, raising the humidity and using a saline spray before bed gets most people through.
Also check your filter. A clogged filter lets more dust and allergens through while making the machine work harder — and a grey filter in hay fever season is a very cheap fix for morning congestion.
Dry, gritty or watering eyes.
This one has a single cause almost every time: air leaking upward out of the top of your mask and blowing across your eyes while you sleep. You may never notice it happening — you simply wake with sore, gritty, watering eyes and assume you're tired.
It's most common with nasal and full face masks where the cushion sits across the bridge of the nose, and it usually appears gradually as a cushion wears, because a hardened cushion loses its seal at the top edge first.
How to fix it
Replace the cushion. Nine times out of ten this is the whole fix. If the cushion is over a month old, start here.
Refit the mask lying down. Fitting a mask while sitting up gives a different seal from the one you need in bed. Put the mask on, lie down in your actual sleeping position, turn the machine on, and adjust from there.
Loosen rather than tighten the top straps. Counterintuitive, but over-tightening pulls the cushion out of shape and opens a gap at the bridge. Many upward leaks improve when the upper straps are eased off slightly.
Consider a mask that doesn't cross the bridge of the nose. Under-the-nose designs such as the AirFit F30i, N30i or P10 route the seal below the nose entirely, which removes the leak path to the eyes.
If your eyes are persistently sore despite a good seal, mention it to your GP or optometrist. Air leaks aren't the only cause of dry eye, and CPAP shouldn't be assumed to be the culprit if the obvious fixes don't resolve it.
Red marks, sore spots and irritated skin.
Pressure marks across the bridge of the nose, the cheeks or the forehead are nearly always the result of straps being tighter than they need to be — and the reason they're too tight is usually that the cushion stopped sealing properly weeks ago and tightening was the instinctive fix.
The cycle is predictable: cushion hardens, seal degrades, you tighten, marks appear, you loosen, leaks return, you tighten again. The way out is to replace the cushion rather than adjust around it.
A few other things that help: wash your face before bed and skip night-time moisturiser, since facial oils both degrade silicone and make skin more prone to irritation. Mask liners can protect sensitive skin, though they're a comfort aid rather than a seal fix. And if silicone irritates your skin generally, a memory foam cushion such as the AirTouch range is often noticeably kinder — bearing in mind foam cannot be washed and must be replaced monthly.
Anything that breaks the skin, blisters, or doesn't recover during the day needs attention rather than tolerance — speak to your clinic, since an open pressure sore can take weeks to heal and may mean the mask style isn't right for your face shape.
We've covered this one in more depth separately, including how to refit each mask type and what to do about marks that have already appeared.
Noise, nosebleeds, sinus pain and odd dreams.
A machine that's got louder
Modern machines are close to silent. If yours has become noticeably noisier, the usual cause is a clogged filter making the motor work harder, or a leak turning into a whistle. Check the filter first, then the mask seal and the hose connections at both ends. A genuine change in motor noise on a machine over about five years old is worth mentioning to your provider.
Nosebleeds
Light nosebleeds usually mean the air is too dry and the nasal lining is cracking. Raise the humidity a step and use a saline spray. Recurrent or heavy nosebleeds are not something to manage at home — see your GP.
Sinus pressure or ear discomfort
A feeling of fullness in the sinuses or ears can occur, particularly during a cold when the eustachian tubes aren't equalising normally. It usually settles as the cold does. Persistent sinus pain or any ear pain should be assessed rather than endured.
Vivid dreams
Many people report unusually intense dreams in the first weeks of CPAP. This is generally a good sign rather than a side effect: untreated apnoea fragments sleep and suppresses REM, and effective therapy lets REM rebound. It typically settles within a few weeks as your sleep architecture normalises.
Waking more often at first
Adjusting to a mask genuinely does disturb sleep initially, and it's common to wake when turning over for the first week or two. If it hasn't improved after a month, treat it as a fit problem rather than an adaptation problem — something about the mask is waking you, and it's usually a leak or a tube pulling.
Symptom, likely cause, first thing to try.
| Symptom | Most likely cause | First thing to try |
|---|---|---|
| Dry mouth, sore throat | Mouth opening in sleep, or a mask leak | New cushion, then humidity up one step, then a chin strap |
| Bloating, burping, wind | Air entering the stomach (aerophagia) | Sleep on your left, raise the bed head; ask the clinic about EPR |
| Blocked, crusty nose | Air too dry | Humidity up one step, saline spray, check the chamber isn't empty |
| Streaming nose, hose gurgling | Too much humidity, or rainout | Humidity down a step, raise tube temperature, lower the machine |
| Dry, gritty eyes | Air leaking upward past the nose bridge | New cushion, refit lying down, ease off the top straps |
| Red marks, sore nose bridge | Straps over-tightened to compensate for a worn cushion | New cushion, then reset strap tension from scratch |
| Machine sounds louder | Clogged filter, or a leak whistling | New filter, then check mask seal and both hose ends |
| Light nosebleeds | Nasal lining too dry | Humidity up a step plus saline spray; see your GP if recurrent |
| Waking repeatedly | Leak, or tubing pulling as you turn | Refit the mask; consider a top-of-head tube mask or hose lanyard |
| Vivid dreams | REM rebound — therapy working | Nothing; usually settles in a few weeks |
Notice how often "new cushion" is the first step. It's the cheapest item in your setup and the cause of a disproportionate share of these symptoms.
When to stop adjusting and call your clinic.
Most side effects are yours to solve with a cushion, a setting and a bit of patience. These are not.
That last one matters more than it looks. Sleep clinics would far rather adjust your settings or try a different mask than discover a year later that you quietly gave up. Abandoning CPAP is the one outcome with real health consequences, and it's almost always avoidable — most people who stop did so over a problem that had a straightforward fix nobody had told them about.
Six things people get wrong about CPAP side effects.
What actually solves each one.
Look back at the table: "new cushion" is the first step for dry mouth, dry eyes, red marks and night waking. A hardened cushion leaks, and a leak causes most of the symptoms in this guide. If yours is over a month old, replace it before changing any setting.
If your mouth falls open in sleep, or you're congested often enough that nasal therapy keeps failing, a full face mask covers both nose and mouth and removes the problem entirely. Under-the-nose designs such as the F30i also avoid the bridge-of-nose seal that causes eye irritation.
Stretched headgear is why straps end up over-tightened, and over-tightening is behind both pressure marks and upward leaks into the eyes. When you fit new headgear, reset the tension from scratch rather than matching your old setting, or you'll be too tight from the first night.
Dry nose, blocked nose and rainout are all humidity problems, and a scaled or cloudy water chamber won't deliver humidification properly however high you set it. Heated tubing is the proper fix for rainout, because it stops the air cooling and condensing on the way to your mask.
A clogged filter makes the machine louder, lets more dust and pollen through, and contributes to morning congestion. It costs almost nothing and takes seconds to change, which is exactly why it's the part most often forgotten for months at a time.
Quick answers on CPAP side effects.
How do I stop dry mouth from CPAP?
Why does CPAP make my stomach bloated?
Why is my nose blocked every morning on CPAP?
Why are my eyes dry and sore after using CPAP?
How long do CPAP side effects last?
Can CPAP damage your teeth?
Should I use a chin strap or a full face mask?
Why has my CPAP machine got louder?
Is it normal to wake up more often when starting CPAP?
When should I contact my sleep clinic about side effects?
More UK-specific CPAP guidance.
This guide is for general educational purposes only and is not a substitute for personalised medical advice. Side effects vary between individuals and can have causes unrelated to CPAP therapy — always follow the instructions supplied with your own equipment and raise persistent symptoms with a qualified healthcare professional.
Never adjust your prescribed pressure settings, EPR or ramp settings yourself. If your symptoms are severe, worsening, or making you consider stopping therapy, contact your sleep clinic or CPAP provider rather than changing your treatment independently.
