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A sleeping baby is one of the calmest sights for new parents. When your little one is at rest, you can examine those little fingers and toes. You can soak in their sleepy eyes and wiggly nose. You love all those tiny grunts, snores, and their adorable open mouth.

But hold on — you may want to focus more on that last feature. Mouth breathing during sleep may be a sign of certain upper respiratory issues and can lead to health complications if not treated.

Here’s more about why your baby may sleep with their mouth open, what you can do to help, and when you should visit your pediatrician.

Newborn babies breathe through their noses almost exclusively unless their nasal passage is obstructed in some way. In fact, young babies — until around age 3 to 4 months — haven’t yet developed the reflex to breathe through their mouths. (That is, unless they’re crying.)

Researchers explain that mouth breathing during sleep may develop in response to some type of blockage in the upper airway, like the nose or throat. This could be from something fairly harmless on its own, like a stuffy nose with a cold or from allergies. Or it could be from other, more complex conditions.

Over time, breathing through the mouth may become a habit that’s hard to break.

Thing is, mouth breathing isn’t as efficient as nose breathing — especially when it comes to oxygen absorption in the lungs. And breathing through the nose also helps to filter out bacteria and irritants from entering the body.

Potential causes of mouth breathing include the following:

Mucus

Your baby may be breathing through their mouth out of necessity if their nose is stuffy or blocked with mucus. They may have recently had a cold or might be allergic to something in their environment.

Whatever the case, babies can’t easily clear mucus on their own, so they may compensate with mouth breathing.

Sleep apnea

Mouth breathing is also a sign of sleep apnea, which basically means that your baby’s upper airway is obstructed in some way. With babies and children, this is usually due to enlarged tonsils or adenoids.

Other symptoms include things like snoring, restlessness during sleep, pauses in breathing, and coughing or choking.

Deviated septum

Sometimes mouth breathing can be caused by an abnormality in the cartilage and bone that separates your baby’s nostrils from one another. This may lead to trouble breathing through the nose and may be common in people who also have a narrow upper jaw (also associated with mouth breathing).

Habit

And some babies may just get in the habit of breathing through their noses after sickness or for some other reason.

If your baby seems to struggle to breathe or has other symptoms along with mouth breathing, consider making an appointment with your pediatrician. Your child’s doctor can help rule out conditions that may be blocking the airway, prescribe medication for any infections, or order further testing.

Otherwise, you might try the following things at home to clear congestion:

  • Humidifier. Adding moisture to the air can help stuffy noses. A cool mist humidifier is most appropriate for babies and young children to avoid burn risk. If you don’t have a humidifier, you might consider sitting with your baby in the bathroom while you run a hot shower to create steam.
  • Bulb syringe. Even a small amount of mucus in your baby’s nose can make it hard for them to breathe. You can suck it out using a basic bulb syringe or one of those fancy snot suckers, like the NoseFrida. Be gentle so you don’t hurt your little one’s nose. And clean your syringe with each use to prevent harmful bacteria from forming.
  • Saline wash. A few sprays of a saline solution (salt water) may help thin and loosen the mucus before you suck it out. As your baby gets a bit older, you may even try a neti pot or saline rinse. Just be sure to boil tap water and cool or use distilled water for safety.
  • Stay hydrated. Make sure your baby is drinking plenty of breast milk or formula to avoid dehydration and keep the mucus flowing.

Related: How to treat nasal and chest congestion in a newborn

Baby no longer stuffy? If you still notice mouth breathing during sleep, bring it up to your pediatrician. Enlarged tonsils and adenoids obstruct the upper airways and won’t respond to home treatment. In some cases, they may be infected. In others, they may just be larger due to genetics.

Whatever the case, your doctor can advise you on any testing (such as an overnight sleep study) or next steps you should take.

Medications, like Flonase or Rhinocort, may help with ongoing allergies or in more mild cases of sleep apnea. In other cases, your doctor may recommend surgery to remove the tonsils and/or adenoids or correct other issues, like a deviated septum, that are causing breathing problems.

Treatment options for sleep apnea include things like positive airway pressure therapy with CPAP and BPAP machines. These devices work by blowing air slowly through a mask that your child wears to sleep. The air helps to keep your little one’s airway stay open.

As your child gets older, there are also certain mouthpieces and other oral devices that may or may not help. Rest assured that needing these kinds of interventions for children is rare.

Related: Signs of sleep apnea in adults and children

You might not think that mouth breathing during sleep would have any major consequences. But dentists and doctors say that there are a number of potential discomforts and other issues that could develop if it continues long term.

Side effects include:

  • swollen tonsils
  • dry cough
  • inflamed tongue
  • teeth issues, like cavities
  • foul-smelling breath
  • gingivitis

There are also potential complications, including long face syndrome. This basically means that your child’s lower facial features may disproportionately elongate. Features you may notice include things like:

  • larger chin
  • gingival “gummy” smile
  • open bite
  • overall narrow face

These features can be corrected surgically.

Mouth breathing may also lower the concentration of oxygen in the blood. Over time, this may lead to anything from heart issues to high blood pressure.

And then there’s sleep. Babies and kids who breathe through their mouths during sleep often don’t sleep as deeply as those who breathe through their noses.

There’s actually a link between mouth breathing and symptoms typically associated with attention deficit hyperactivity disorder (ADHD).

In fact, some kids diagnosed with ADHD may instead be dealing with issues from the sleep deprivation resulting from — that’s right — mouth breathing. The signs of both disorders are similar.

So, if you can determine that your child has sleep deprivation due to mouth breathing, you can better treat the underlying issue.

Related: 14 signs of attention deficit hyperactivity disorder

Cute, definitely. But your baby’s mouth breathing during sleep may also be a critical clue to their health.

There are plenty of things you can do to help your baby breathe easier if they’re simply congested. If the issue continues, it’s worth bringing it up to your pediatrician or a dental health professional.

Once you treat any obstructions or other conditions, you can both sleep much more soundly at night.