Nasal vs Mouth Breathing: The Hidden Habit That Shapes Health, Sleep, and Facial Growth

Most parents don’t think twice about how their child breathes, as long as they are breathing, right? But whether that breath moves through the nose or the mouth changes everything.

From jaw development to sleep quality, behavior, focus, and even immune function, the route of our breath plays a major role in how the body grows and performs. Once you learn what to look for, you’ll start noticing it everywhere. You’ll be able to glance at someone and instantly tell whether they’re breathing properly or relying on mouth breathing.

Let’s unpack what the research says about nasal vs. mouth breathing, how it affects jaw and airway development, and how parents can identify and correct early signs before they become lifelong problems.

This guide is a collab with Alex (@thenaturalmindedmama), who has experience working in the field of functional and holistic dentistry!

As always, this is for educational purposes only, not medical advice,

Why Nasal Breathing Is the Body’s Design

Nasal breathing is the physiological default. It’s how we’re meant to breathe 95% of the time, especially at rest and during sleep. The nose is not just an air hole; it’s a filtration, humidification, and pressurization system designed for optimal oxygen exchange.

Here’s why nasal breathing matters:

1. Filtration & humidification: The nose filters dust, pathogens, and pollutants while humidifying and warming incoming air protecting the lower airways from dryness and irritation. Mouth breathing bypasses this natural filter, increasing respiratory irritation and inflammation.

2. Nitric oxide production: The nose and sinuses make a gas called nitric oxide, which helps your body use oxygen more efficiently, opens blood vessels for better circulation, and helps fight germs (antimicrobial properties).

   • Nitric oxide produced in the nasal passages supports improved oxygen delivery and airway dilation, which does not occur with mouth breathing

3. Better CO₂ regulation and diaphragm use: Nasal breathing naturally encourages slow, deep breaths from the diaphragm. This helps maintain balanced carbon dioxide (CO₂) levels, allowing oxygen to be released more efficiently into your tissues, a process known as the Bohr effect. 

   • In contrast, mouth breathing often leads to shallow, rapid breathing that lowers CO₂ too much, which can leave you feeling anxious, tired, and less oxygenated overall.

4. Postural stability: Nasal breathing naturally engages the diaphragm and core muscles, supporting healthy spinal alignment and reducing tension in the neck and shoulders, particularly in growing children.

5. Encourages proper tongue placement. The tongue should be resting against the roof of the mouth, behind the upper front teeth. Mouth breathing forces the tongue to drop down. 

   • FAQ: “What if my child sleeps with their mouth open, but is breathing through their nose?” 

   • Answer: Always check the tongue. If the mouth is open, most likely the tongue has dropped down, and is not in proper placement. 

How Mouth Breathing Changes the Face and Jaw

If a child chronically breathes through their mouth, especially during sleep, the effects are visible 

Altered Craniofacial Growth

Chronic mouth breathing during childhood leads to changes in how the jaw and facial bones grow. Instead of growing forward and wide (as intended), the face tends to grow downward and narrow. The tongue is the palate's natural expander. If a child is mouth breathing, their tongue is going to drop downward and not provide the "natural expansion” it’s designed to do which causes the narrow face.

This pattern, often referred to as “adenoid facies”, is characterized by:

• Long, narrow face

• Open mouth at rest

• High, arched palate

• Crowded or crooked teeth

• Forward head posture

• Dark circles under the eyes

A systematic review in Frontiers in Public Health (2022) confirmed that mouth breathing is linked with abnormal dentofacial development, narrow dental arches, and increased malocclusion (PMID: 36159237).

Another review in Children (Basel) (2023) found that prolonged nasal obstruction and mouth breathing cause measurable craniofacial changes, even in the absence of significant tonsil or adenoid enlargement (PMID: 37628425).

A 2025 orthodontic study reinforced these findings, showing consistent correlations between mouth breathing, crossbites, high palates, and airway narrowing (PMID: 39857903).

The Sleep Connection: How Mouth Breathing Impacts the Brain and Body

When the mouth opens during sleep, the tongue drops from the palate, the airway narrows, and oxygen delivery becomes less efficient. This pattern often leads to sleep-disordered breathing (SDB) and, in more severe cases, obstructive sleep apnea (OSA). If you receive a sleep study and it is negative for obstructive sleep apnea, it does not necessarily mean that you do not have sleep disordered breathing. You may need to seek out a new, truly airway focused provider. Let’s break down OSA and UARS. 

• Obstructive Sleep Apnea (OSA) and Upper Airway Resistance Syndrome (UARS) are both sleep-related breathing issues, but they show up in different ways. OSA happens when the airway becomes blocked during sleep, causing pauses in breathing or very shallow breaths. This often leads to loud snoring, noticeable breathing pauses, drops in oxygen levels, and daytime sleepiness. It’s also linked to higher risks for things like high blood pressure, heart problems, and stroke. OSA is what is picked up during a sleep study.

• UARS, on the other hand, is a bit different. Instead of full pauses in breathing, the airway becomes narrower and more resistant, making it harder to breathe smoothly. This doesn’t usually cause oxygen drops, but it does cause frequent sleep disruptions. People with UARS may not snore as loudly and may not seem “sleepy” during the day, but they often feel exhausted, unrefreshed, or struggle with insomnia-like symptoms.

• Sleep studies do not typically pick up on UARS. If a study comes back negative for OSA, UARS could still be a factor. If left untreated UARS will, most times, turn into sleep apnea. If a provider is not properly trained in airway disorders (most aren't), then this often goes overlooked.

Research consistently links chronic mouth breathing to poor-quality sleep and neurobehavioral symptoms in children including inattention, hyperactivity, emotional dysregulation, and learning difficulties.

• In one landmark pediatric study, children with mild sleep-disordered breathing showed significant behavioral and cognitive impairments compared to healthy peers (PMID: 14737917).

• Another study found that chronic snoring and mouth breathing in children were associated with lower school performance and daytime fatigue (PMID: 9738185).

For adults, mouth breathing during sleep has been linked to worsened sleeping disorder severity and increased cardiovascular strain. 

Behavioral Symptoms and Misdiagnoses

Because the brain depends on uninterrupted oxygen flow for proper attention and regulation, children with even mild sleep-disordered breathing often show behavioral symptoms that mimic conditions like ADHD, anxiety, or sensory processing disorders. In many cases, these behaviors aren’t caused by brain chemistry at all, they’re the body’s response to disrupted sleep and not getting enough oxygen during the night!

Common behavioral signs that may be linked to poor sleep or mouth breathing include:

• Acting impulsively or having trouble thinking before responding

• Difficulty focusing or paying attention 

• Big emotional reactions or frequent mood swings

• Getting frustrated easily

• Constant movement, fidgeting, or restlessness during the day

All of these symptoms overlap with ADHD criteria! Several studies have shown that a significant percentage of children diagnosed with ADHD symptoms actually had underlying sleep-disordered breathing, and treatment of the airway issue often led to dramatic improvements in focus, behavior, and mood.

• The AAPD recognizes that children with untreated obstructive sleep apnea may be inappropriately diagnosed with ADHD. Even the National Resource Center on ADHD acknowledges that ADHD may be associated with a state of increased sleepiness rather than hyperactivity. 

• If you wanted to break down why this is the case: if a child has a sleep disorder and is chronically tired, their body will naturally stimulate itself in order to stay awake (hence the ADHD symptoms). If that child is then given ADHD medication which is A STIMULANT the fire is just being fueled. They don’t need a stimulant. Their body is already over-stimulated. They need sleep, and they need to be able to BREATHE to get that sleep. 

This overlap highlights the importance of evaluating breathing patterns and sleep quality before assuming a behavioral or psychiatric diagnosis. Sometimes, the “hyperactive” or “defiant” child is simply a chronically exhausted one who hasn’t been getting restorative sleep.

Oral Health and Systemic Effects

When you breathe through your mouth, your saliva dries out and that’s a big problem. Saliva helps keep the mouth’s pH balanced, supports healthy bacteria, and protects your enamel from decay

Chronic mouth breathing leads to:

• Dry mouth (xerostomia)

• Increased dental caries (cavities)

• Gingivitis and gum recession

• Halitosis (bad breath)

• An overgrowth of unhealthy bacteria in the mouth

• Chapped lips

Why People Mouth Breathe: Getting to the Root Cause

Mouth breathing isn’t a random habit; it’s often a sign of an obstruction or dysfunction somewhere in the airway.

Common Causes by Age Group

Infants and Toddlers

• Tongue or lip tie: Tight oral tissues can make it hard for babies to close their lips or keep their tongue on the palate, leading to open-mouth breathing.

  • Link to a full tongue tie guide

• Poor latch or frequent milk dribbling: Often a sign that baby isn’t creating a proper seal or has difficulty coordinating suck–swallow–breathe patterns.

  • This can also be a sign of a tongue tie, or tension that CST can help with

• Chronic congestion or reflux: Stuffy noses or acid reflux can make nasal breathing uncomfortable, so babies default to mouth breathing.

Children

• Allergic rhinitis or chronic sinus congestion: Seasonal allergies or constant stuffiness block nasal airflow and encourage open-mouth breathing.

• Enlarged adenoids or tonsils: Swollen tissue at the back of the throat can narrow the airway and force the mouth open during rest or sleep. 

  • This doesn’t necessarily mean the removal of tonsils/adenoids in the solution. The question is - WHY are they enlarged?

• Deviated septum or narrow nasal passages: Structural issues can limit airflow through one or both nostrils, making nasal breathing difficult.

Teens and Adults

• Lingering airway restrictions from childhood: If mouth breathing wasn’t corrected early, the airway may remain narrow or underdeveloped.

• Structural changes: A small jaw, high palate, or deviated septum can reduce nasal space and airflow.

• Chronic allergies or inflammation: Persistent congestion or sinus inflammation can block nasal breathing.

• Postural habits: Forward head posture and time spent on screens can keep the mouth slightly open and the tongue low in the mouth, reinforcing the habit of mouth breathing.

Some other possible causes:

• Nasal polyps

• Habitual patterns 

• Obesity

• Asthma

• Underdeveloped jaws

• Narrow palate

• Sleep breathing disorder

• Nasal congestion

• Allergies

• Food sensitivity

• Asthma 

**Before retraining someone to nasal breathe, you must make sure they physically can! If the airway is blocked, forcing nasal breathing (or taping the mouth shut) can worsen oxygen deprivation. It’s also a temporary band-aid. You need to get to the root cause of why someone isn't nasal breathing.

Correcting Mouth Breathing: Prevention and Treatment

1. Clear the Nose and Airway

The first step is to address why the person can’t breathe through their nose:

• Airway dentist evaluation for adenoids, tonsils, or septal deviation 

  • A provider or pediatrician may refer you to an ENT, but they often do not address root cause care. An airway dentist is often a better choice for this evaluation

• Allergy management or desensitization therapy

• Saline rinses or nasal hygiene routines

• Humidifiers and air purifiers for clean, moist air

  
  

2. Support Proper Oral Function and Posture

Once the airway is clear, the next step is retraining oral posture.

• MYOFUNCTIONAL THERAPY

  • An airway dentist will refer. They will teach you how to retrain all the below.

• Tongue up (resting on the roof of the mouth)

• Lips closed

• Teeth slightly apart

• Nasal breathing

If assessing a child, pull down on the jaw while they are sleeping to see if their tongue is resting on the roof of their mouth. 

Orofacial Myofunctional Therapy (OMT) is one of the most effective evidence-based methods for correcting mouth breathing habits. Studies show that OMT can improve tongue posture, lip seal, and sleep-disordered breathing when combined with medical or orthodontic care.

Functional dentistry and orthodontics can also play a key role. Palatal expansion in growing children has been shown to widen the nasal cavity and improve airflow.

3. Lifestyle & Habit Retraining

Encourage gentle, consistent nasal breathing practice throughout the day. For kids, simple reminders like:

“Tongue up, lips closed, healthy breathing through the nose.” - Hal Stewart, DDS, FACD. @halstewartdds on insta

Reduce screen-related posture issues, ensure a clean sleep environment, and teach mindful breathing during reading or quiet play.

4. Mouth Taping:

Mouth taping has become a popular tool for encouraging nasal breathing during sleep and can be a helpful part of improving sleep quality and oxygenation. The goal isn’t to “force” nasal breathing, but to remind the body to keep the lips sealed and the tongue on the palate once the airway is clear.

Benefits:

• Reduce snoring by keeping the tongue from falling back and blocking the airway

• Encourage nasal breathing, which supports nitric oxide production and oxygen efficiency

• Improve sleep quality by promoting steadier breathing and fewer awakenings

• Relieve dry mouth and protect dental health by maintaining moisture overnight

• Enhance morning alertness by reducing overnight oxygen drops and sleep disruptions

When paired with nasal hygiene, allergy management, and good sleep posture, mouth taping can serve as a simple, low-cost training tool to restore healthy breathing patterns.

Mouth Taping May Be Helpful For:

• Adults who can comfortably breathe through their nose during the day

• People who snore lightly or breathe through their mouth at night but do not have moderate to severe sleep apnea

• Individuals with a clear airway (no nasal congestion)

• Those wanting to retrain tongue and lip posture for better nasal breathing habits

• People looking to reduce morning dry mouth or throat irritation

Mouth Taping Is Not Recommended For:

• Anyone who cannot breathe easily through their nose due to obstruction, congestion, or deviated septum

• Children, since they can’t always communicate distress or remove tape safely

• Individuals with moderate to severe obstructive sleep apnea or respiratory conditions (e.g., asthma, COPD)

The Parent Screening Checklist

Use this quick screening tool to help parents (or yourself) spot possible signs of chronic mouth breathing or airway dysfunction at home.

Observe Your Child:

Baseline screening for parents by Hal Stewart, DDS, FACD. (@halstewartdds on insta)

Observe your child for 5-10 minutes every hour for 3 hours in a row for 5 nights. Make note of what you see, or even better video it!

• Are they sleeping on their stomach or back?

• Mouth or nasal breathing?

• Snoring?

• Drooling?

• Tossing and turning? Restless?

• In odd positions?

• Noisy breathing?

Discuss results with an airway-focused pediatric dentist, or myofunctional therapist. 

How to Find a Local Airway Provider:

Click this link for a local list of airway providers

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Nasal breathing is one of the simplest, most powerful foundations of lifelong health and it starts in childhood.

When the lips are closed, the tongue rests on the palate, and air flows through the nose, you’re supporting wide jaw growth, restful sleep, better oxygenation, stronger immunity, and even emotional stability.

When that pattern shifts toward mouth breathing, it’s a signal that something deeper needs to be addressed.