CPAP Side Effects: What's Normal, What Isn't, and What to Do

Most CPAP side effects are fixable, often with a setting change or a $20 part swap. They get labeled "side effects" but they're closer to setup problems — symptoms that go away when the underlying mechanical or environmental issue is addressed. This article runs through the seven most common, ranked by how often we hear about them, with the actual fix for each.

1. Dry mouth and dry throat

The most common side effect, by a wide margin. Wake up with a mouth that feels like cotton, a throat that's sore for the first few hours, and dehydrated lips. Three possible causes:

Mouth breathing

If you use a nasal pillow or nasal mask and your mouth opens during sleep, the pressurized air bypasses your nose entirely and exits your mouth — taking moisture with it. The classic dry-mouth-with-nasal-mask pattern. Fix: chinstrap, mouth tape, or switch to a full-face mask. Full guide: mouth breathing on CPAP.

Insufficient humidification

If your humidifier is off or set too low, the pressurized air is much drier than ambient room air. Solution: turn the humidifier up incrementally (one level per night until the dry mouth resolves) and consider heated tubing if condensation becomes a problem at higher humidity settings.

Bedroom air is very dry

In winter (especially with forced-air heating), ambient humidity in many bedrooms drops below 30%. The CPAP humidifier can only compensate so much. A bedroom humidifier — separate from the CPAP — running overnight is the cheapest fix.

2. Nasal congestion

Some users develop chronic stuffiness within weeks of starting CPAP. Counter-intuitive — the pressurized air is supposed to open the airway, not close it. Common causes:

• The air is too dry. Dry air irritates nasal mucosa, which responds by producing more mucus. Turn the humidifier up.
• The air is too cold. Cold dry air is the worst combination. Use heated tubing if your machine supports it.
• The filter is overdue. Allergens passing through a loaded filter compound nasal inflammation. Replace if you haven't recently — filter cadence guide here.
• You have allergies. CPAP doesn't cause allergies, but it can intensify existing ones because you're now consistently breathing through your nose for 7+ hours. Switch to hypoallergenic filters as a first step.

Saline nasal rinse (NeilMed Sinus Rinse, or a basic bulb syringe with saline) before bed is helpful for chronic CPAP congestion. The NIH has guidance on safe technique — use distilled or boiled water, not tap.

3. Aerophagia (air in the stomach)

Swallowing air during CPAP use ends up in your stomach. Symptoms: morning bloating, belching, stomach discomfort, occasional gas pain. Affects about 30% of CPAP users, varying severity.

Causes

• Pressure too high. The single most common cause. The pressure your doctor prescribed may exceed what you actually need, especially during earlier (lighter) stages of sleep.
• Sleep position. Back-sleeping accelerates aerophagia; many users find side-sleeping reduces it.
• Eating close to bedtime. Stomach content + swallowed air = more discomfort.

Fixes

• If using fixed-pressure CPAP, ask your doctor about switching to APAP (auto-CPAP), which lowers pressure when full pressure isn't needed.
• If on APAP already, ask about lowering the minimum pressure setting.
• Sleep on your side; raise the head of your bed slightly.
• Don't eat in the 2 hours before bed.

Aerophagia usually improves once pressure is right. If it doesn't, BiPAP (which delivers different pressures for inhale vs. exhale) often solves it for stubborn cases.

4. Skin irritation and mask marks

Red marks on the bridge of the nose, cheeks, or chin in the morning are very common in the first few weeks. They almost always indicate:

• Over-tightened headgear. The cushion is being mashed into your skin rather than gently sealing. Loosen the straps and see if the seal still holds — most masks need much less tension than users default to.
• Wrong cushion size. A too-large cushion forces you to over-tighten to seal it; a too-small cushion presses into specific facial points. See our mask sealing guide.
• Skin sensitivity to silicone. Rare. If marks turn into actual rashes or breakouts, ask about a hypoallergenic mask liner — a cloth interface between cushion and skin.

5. Eye irritation

Air leaking upward from the mask blows on the eyes — over time, this dries the cornea and produces morning eye irritation. Always indicates an upward leak from a poorly-sealed mask. Specifically:

• Cushion is too small (leaks out the top of the nose bridge).
• Cushion is worn out.
• Strap tension is uneven (the upper straps need slight adjustment).

Fix the leak. The eye symptoms resolve within days.

6. Claustrophobia

Less a side effect than a tolerance challenge, but real. The mask covering your face triggers a stress response in some users — especially those new to therapy. Practical approaches:

• Wear the mask awake. Spend 15-30 minutes per day wearing the mask while watching TV or reading, without the machine running. Builds tolerance gradually.
• Use the ramp feature. Most modern CPAPs start at a low pressure (4-6 cmH₂O) and ramp up over 15-45 minutes. The lower starting pressure feels much less invasive.
• Try a smaller mask. Nasal pillows feel less enclosing than full-face masks. The AirFit P10 is the least-claustrophobic mask on the market for most users.

7. Difficulty exhaling

Some users feel like they're pushing against the airflow when they exhale, particularly at higher pressures. CPAP delivers a single pressure throughout the breath cycle, which creates this sensation.

Two fixes:

• Turn on EPR (Expiratory Pressure Relief) if your machine has it. ResMed AirSense and AirCurve machines do; the setting drops pressure slightly during exhalation. Default is usually 0; try level 2 or 3.
• BiPAP instead of CPAP. BiPAP machines use two separate pressures (higher for inhale, lower for exhale), which feels dramatically more natural at high pressures. Requires a prescription change.

What's not a normal CPAP side effect

Some symptoms aren't fixable with settings and shouldn't be ignored:

• Chest pain during CPAP use. Stop therapy and call your doctor.
• Coughing up blood or bloody nasal discharge. Could indicate pressure too high, irritation to nasal tissue, or unrelated medical issue. Doctor visit.
• Persistent sore throat lasting weeks despite humidifier adjustments. Could indicate equipment hygiene issue or unrelated infection.
• Worsening daytime sleepiness on CPAP. Your therapy may be inadequate. Check your reported AHI; if it's elevated, see our AHI guide and consider a re-titration.

Bottom line

CPAP side effects are usually setup problems in disguise. Mask too tight. Pressure too high. Air too dry. Filter overdue. Each has a specific, cheap fix. Before assuming the therapy isn't for you, run through this list — almost all of them resolve once the right adjustment is made.