Dry mouth at night when sick: why colds and flu dry you out

Waking up with a mouth like sandpaper is one of the less talked-about parts of a cold or flu. It usually has a few causes stacked on top of each other: a blocked nose that sends you to mouth breathing, a fever that dries you out, and the cold remedies you took to feel better. The good news is that each one has a simple fix, and the dryness normally clears up as you recover.

Why do you get dry mouth at night when you're sick?

You get dry mouth at night when you're sick because illness hits several of the main causes of dry mouth at once. The NHS lists dehydration, including from being ill, along with medicines and breathing through your mouth at night because of a blocked nose, among the main causes. A cold or flu can bring all three in the same week.

Saliva does more than keep your mouth comfortable. The National Institute of Dental and Craniofacial Research (NIDCR) explains that saliva contains minerals that help keep teeth strong and fight tooth decay, and that a dry mouth raises the risk of decay and fungal infections because saliva helps keep harmful germs in check. That's one reason to take night-time dryness seriously even when it feels minor.

Here's how the main causes compare:

Our general guide to waking up with a dry mouth covers causes that have nothing to do with being sick.

How does a blocked nose cause dry mouth at night?

A blocked nose causes dry mouth at night because it pushes you to breathe through your mouth while you sleep. The NHS lists breathing through your mouth at night as a main cause of dry mouth, and says it can happen if you have a blocked nose or sleep with your mouth open.

The NHS lists a blocked or runny nose as one of the main symptoms of a cold, and says decongestants can also help with flu, hay fever and sinusitis. It also notes that young children with a cold may breathe through their mouths and have trouble sleeping. Our guide to how to sleep with a stuffy nose has practical ways to get more air through your nose at bedtime.

Can a fever make your mouth dry?

A fever can make your mouth dry by making dehydration more likely. The NHS lists a high temperature as one of the things that makes dehydration happen more easily, and it lists a dry mouth, lips and tongue among the symptoms of dehydration. Being sick to your stomach or having diarrhoea adds to the fluid you lose.

The NHS usually considers a temperature of 38C or above to be high. Its advice for a fever is to rest and drink plenty of fluids, with water best, so that your pee is light yellow and clear. When you've barely eaten or drunk all day and then sleep for eight hours, it's easy to wake up dry. A glass of water by the bed makes night-time sips easy, which is something the NHS suggests for dry mouth anyway.

Can cold and flu medicines cause dry mouth?

Cold and flu medicines can cause dry mouth, especially those containing decongestants or antihistamines. The NHS lists a dry mouth as a possible side effect of decongestants. It also lists dry mouth as a side effect of both drowsy and non-drowsy antihistamines, which turn up in many night-time cold remedies.

The NHS notes that many cold products are sold as all-in-one remedies combining a decongestant, a painkiller or an antihistamine, and it says not to use more than one medicine for a blocked nose at the same time. Decongestant sprays and drops shouldn't be used for more than 5 days at a time, because longer use can make stuffiness worse. Decongestants also aren't suitable for everyone without advice, including people with high blood pressure, diabetes, heart problems or glaucoma, and they shouldn't be given to children under 6.

Side effects from decongestants usually go away once you stop taking them, according to the NHS. If you take a prescribed medicine and think it's drying your mouth, the NHS says not to stop it without medical advice. Our list of medications that cause dry mouth covers other common ones, and our article on decongestant spray rebound explains the 5-day limit.

What helps dry mouth at night when you're sick?

What helps most is drinking regularly, easing the blocked nose and keeping the bedroom air from getting too dry. The NHS suggests sipping cold water through the day, keeping water by your bed at night, sucking ice cubes or sugar-free sweets, and using lip balm if your lips are dry. It suggests avoiding lots of alcohol, caffeine and fizzy drinks.

The NIDCR adds that caffeine can dry out the mouth and lead to dehydration, that tobacco and alcohol dry the mouth too, and that a humidifier at night can help relieve dry mouth. If you use one, the EPA says not to humidify above 50% indoor humidity, and to empty, dry and refill portable humidifiers daily. Our guide to using a humidifier for sleep covers setup.

For the blocked nose, the NHS suggests breathing in steam, such as sitting in the bathroom with a hot shower running, and a pharmacist can advise on decongestants. Children shouldn't breathe steam from a bowl of hot water because of the risk of scalding. For more ideas, see our list of dry mouth at night remedies and our article on whether drinking water before bed helps.

Keep brushing too. The NHS suggests brushing twice a day and using an alcohol-free mouthwash when your mouth is dry, since you're more likely to get tooth decay.

Should you use mouth tape for dry mouth while you're congested?

You shouldn't use mouth tape while you're congested. Mouth tape only works for dry mouth when you can breathe comfortably through your nose, and a cold or flu usually takes that away. Cleveland Clinic's sleep specialist says never to use mouth tape with nasal congestion, nasal obstruction, chronic allergies or a sinus infection.

A 2025 systematic review in PLOS One found that four of the ten studies it included warned that keeping the mouth closed could pose a serious risk of asphyxiation if the nose is blocked or the person vomits. Both are more likely when you're ill. Put the tape away for now.

Once you've recovered and your nose is clear again, mouth tape can be a good option if mouth breathing keeps drying your mouth at night. Close your mouth and breathe through your nose for a couple of minutes first; if that feels easy, you're ready. We don't recommend mouth tape for children. Our articles on mouth tape with a cold and mouth tape for dry mouth cover when and how to start again.

When is dry mouth a sign you need a doctor?

Dry mouth while sick is a sign you need a doctor when it comes with other signs of dehydration that don't improve with drinking. The NHS says to get urgent advice if you feel unusually tired, feel dizzy when you stand up and it doesn't go away, have dark yellow pee or are peeing less than normal, or are breathing quickly or have a fast heart rate.

The NHS says to call emergency services or go to A&E if someone with signs of dehydration has blue, grey, pale or blotchy skin, lips or tongue, skin that feels cold, difficulty breathing, confusion, or is very sleepy and difficult to wake. These can be signs of shock. Babies, children and older adults are more at risk of dehydration, according to the NHS.

For a cold, the NHS suggests seeing a GP if you have a high temperature for more than 3 days, your symptoms get worse, you feel short of breath, or symptoms haven't improved after 10 days. If your dry mouth carries on for a few weeks after you've recovered, even with home and pharmacy treatments, the NHS says to see a GP, who can look for other causes such as medicines or conditions like diabetes. Our article on dry mouth at night and diabetes explains that link.

Our pick (paid partner): Titan Bamboo Silk Mouth Tape

For when you're well again and mouth breathing is still drying your mouth at night, our pick is Titan Bamboo Silk Mouth Tape. It's for clear-nose nights only, not while you're congested. We haven't tested or ranked mouth tapes ourselves; this is our recommendation.

Titan says the strip is bamboo silk rather than kinesiology tape and describes it as soft, breathable and moisture-wicking. It's one oval size, 76 by 38 mm, worn horizontally across the lips. Titan suggests 20 to 30 minutes of daytime practice before the first night, says every batch is third-party tested and certified PFAS-free, and offers a 30-night guarantee that refunds you if your sleep isn't better.

Read next

• Why do I wake up with a dry mouth?
• Snoring when sick: why a cold makes you snore
• Medications that cause dry mouth

* This content is for informational and educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease or health condition. Talk to a qualified healthcare provider about your health.