Up to 70% of CPAP users report dryness in their mouth, nose, or throat, and nasal congestion is one of the most common reasons people stop using their machine. The good news: most CPAP-related congestion is preventable with the right combination of humidity, mask fit, and nasal care. Here’s what causes it and how to fix it.
Why CPAP Causes Nasal Congestion
The pressurized air your CPAP delivers pulls moisture out of your nasal passages as it flows through. This evaporation increases the concentration of fluid surrounding cells in your nasal lining, which triggers those cells to release inflammatory compounds. The result is swelling, stuffiness, and irritation that can feel like a permanent cold.
Mouth leaks make this worse. When your mouth falls open during sleep, the pressurized air takes a shortcut out through your mouth instead of staying in a closed circuit. This dramatically increases the volume of dry air passing over your nasal tissue and causes nasal airway resistance to spike. If you wake up with a dry mouth and a stuffy nose, mouth leak is likely a major contributor.
Use Heated Humidification
A heated humidifier is the single most effective tool for preventing CPAP-related congestion. It adds warm moisture to the air before it reaches your nose, replacing what the pressurized airflow strips away. Most modern CPAP machines either include a built-in humidifier or accept one as an attachment. If yours has one and you’re not using it, turn it on. If it’s already on but you’re still congested, try increasing the humidity setting gradually until your symptoms improve.
One common frustration with humidification is “rainout,” where warm, moist air cools inside the tubing and condenses into water droplets that collect in your mask or splatter your face. Heated tubing solves this by keeping the air temperature consistent from the humidifier to your mask, preventing condensation from forming. Heated tubing is especially helpful if your bedroom runs cool, since the temperature difference between the warm humidified air and the cold tube is what causes rainout in the first place. If heated tubing isn’t an option, running the tube under your blanket can help keep it warm.
Choose the Right Mask
Your mask type directly affects how much drying and irritation your nose experiences. Nasal pillow masks, which sit inside the nostrils, deliver pressurized air in a concentrated stream that can increase nosebleeds and nasal dryness. If you’re prone to congestion, a standard nasal mask that covers the nose may distribute airflow more gently.
Full face masks, which cover both the nose and mouth, are often recommended for people who breathe through their mouth during sleep. By capturing mouth leaks within the mask circuit, they reduce the excessive airflow through nasal passages that drives congestion. However, if your congestion is severe enough to block your nose entirely, a full face mask lets you breathe through your mouth without losing pressure. A chin strap is another option for keeping your mouth closed if you prefer a nasal mask.
Regardless of type, a poorly fitting mask leaks air. Leaks around the seal force the machine to increase airflow to compensate, which dries your nasal passages faster. Check your mask fit regularly and replace cushions or pillows when they lose their shape.
Add a Pre-Sleep Nasal Routine
A saline spray or rinse before bed helps hydrate your nasal lining before the CPAP starts pulling moisture out. Saline is just salt water, so it doesn’t carry the risks of medicated sprays. A simple two-spray application in each nostril right before putting on your mask can make a noticeable difference, and you can use it every night without any concern about overuse.
A full saline rinse using a squeeze bottle or neti pot goes further by flushing out allergens, dust, and mucus that may already be narrowing your nasal passages before you even turn on the machine. If you have allergies or live in a dusty environment, this step alone can significantly reduce nighttime stuffiness.
Avoid Decongestant Spray Dependence
Over-the-counter decongestant sprays are tempting because they work fast, clearing a blocked nose in minutes. But they should never become part of your regular CPAP routine. After about three days of use, these sprays cause rebound congestion, where your nasal tissue swells worse than before you started using them. The sprays work by constricting blood vessels in the nose, and repeated use deprives the tissue of blood flow, leading to damage and inflammation.
People who already deal with chronic stuffiness from allergies or a deviated septum are at higher risk. About 1 in 10 people who use decongestant sprays develop rebound congestion, and at that point, stopping the spray can cause headaches and a suffocating feeling that makes it nearly impossible to use CPAP. Reserve decongestant sprays for occasional illness, never for routine CPAP use.
If you need nightly nasal medication, talk to your prescriber about a steroid nasal spray instead. These work through a different mechanism, reducing inflammation without the rebound effect, and are safe for long-term use.
Adjust Your Pressure Settings
Higher CPAP pressures push more air through your nose per breath, which increases drying. If your pressure feels like a wind tunnel, two features can help. Expiratory pressure relief (called EPR on ResMed machines or C-Flex on Philips) briefly lowers the pressure when you breathe out, making exhalation feel more natural. This is especially useful if you need high pressures to keep your airway open, since the blast of air on exhale is often what feels most uncomfortable.
Auto-adjusting CPAP machines (APAP) vary pressure throughout the night based on what you actually need at any given moment. Instead of blasting a fixed high pressure all night, they ramp down during lighter sleep stages when your airway needs less support. Less pressure means less airflow, which means less drying. If you’re on a fixed-pressure machine and struggling with congestion, ask your sleep specialist whether an auto-adjusting machine might be appropriate.
Control Your Sleep Environment
Dry bedroom air compounds the drying effect of CPAP. A room humidifier (separate from your CPAP humidifier) raises the baseline moisture level of the air your machine draws in, giving your CPAP humidifier less work to do. This is particularly important in winter, when indoor heating can drop humidity to desert-like levels.
Keep your CPAP equipment clean. Bacteria and mold growing in a humidifier chamber or tubing can irritate nasal passages and trigger inflammatory congestion that no amount of humidity will fix. Rinse the water chamber daily with warm water and mild soap, and replace the water each night rather than topping off stale water. Wash your tubing weekly and let it air dry completely.
Allergens in your bedroom, including dust mites in bedding, pet dander, and mold, can cause nasal swelling that makes CPAP congestion worse. If you notice your congestion is seasonal or worse after your pet sleeps on the bed, addressing the allergen source may do more than any CPAP adjustment.