Why mouth breathing is bad for your health?

At The Dental Gallery in Melbourne, we routinely screen for correct breathing and tongue position during every 6-monthly preventative examination — because how you breathe affects far more than your nose. Our trusted dentistry focusing on quality sleep is located in Bentleigh East, aims to serves the community near Bayside sururbs. 

The nose filters, warms and humidifies the air you breathe, while mouth breathing leads to chronic irritation of the airway and can result in enlarged adenoids and tonsils in children. For children, teens and adults alike, catching mouth breathing early can prevent years of dental, facial and sleep-related problems.

There are many research studies describing the bad health consequences of mouth breathing.

Here are a few reasons why it is bad to mouth breathe.

Less production of nitric oxide

Nitric oxide is a gas that dilates (makes larger) blood vessels in the body and as a result increases oxygen uptake by the lungs. This gas is made in the sinuses. By breathing through your mouth, you’re missing out on production of this gas and also about 10 to 20% of additional oxygen uptake. As a result, you can compensate by breathing a bit faster and breathing off carbon dioxide. This can cause your carbon dioxide levels to drop, raising blood pH levels, and preventing oxygen from being released as easily to your body’s tissues.

It can cause crooked teeth

Breathing through your mouth prevents your face and jaw from developing properly. Inadequate jaw development can lead to crowding of your teeth and even narrowing of the upper airway. For children, one of the biggest causes of teeth crowding is habitually breathing through the mouth rather than the nose.

One extreme example is often referred to as “Adenoid Facies”, which results in an open mouth and forward head posture, long, narrow face, high arched hard palate, recessed lower jaw, and chronic nasal congestion. Having a smaller jaw can make you much more susceptible to future sleep-related breathing disorders.

It can lead to dental cavities

Mouth breathing leads to you having less saliva and a dry mouth. Saliva reduces acid levels, and can help to prevent plaque build-up. Mouth breathing can also cause you to have bad breath.

Mouth breathing can cause your tongue to fall backwards in your mouth

Ever wondered why it’s harder for you to breathe when lying down in a dentist’s chair with your mouth wide open? Opening your mouth causes your tongue to fall back, preventing proper breathing and in severe cases can obstruct the airway. For adults, the changes to the airway introduced by mouth-breathing while sleeping can give rise to snoring and sleep apnoea.

Concerned? Here are some signs of mouth breathing:

• Dry lips
• Having an open mouth posture
• Dry mouth with inflamed gums
• A long and narrow face
• Narrow high arched palate
• Crowded teeth or lack of spacing between baby teeth
• Enlarged tonsils
• Having a forward head posture

Some Common causes of mouth-breathing are:

• Allergies
• Chronic colds and sinus infections
• Enlarged adenoids and/or tonsils
• Nasal polyps
• Deviated nasal septum

How is mouth breathing diagnosed?

Mouth breathing is often picked up before a patient even mentions it. At The Dental Gallery, Melbourne diagnosis typically involves:

• Clinical screening during routine 6-monthly check-ups — assessing tongue posture, palate shape, tonsil size and facial growth patterns.
• ENT referral to investigate nasal obstruction, allergies, a deviated septum, or enlarged adenoids/tonsils.
• Sleep assessment — if snoring, restless sleep or daytime fatigue is present, a referral for a sleep study (polysomnography) may be recommended to rule out obstructive sleep apnea.
• Airway-focused orthodontic assessment — evaluating jaw width, dental arch shape and bite to identify early intervention opportunities in children.

So what can be done to address mouth-breathing?

At the dental gallery we take an integrative approach to mouth breathing and work with Ear Nose and Throat (ENT) specialists and medical professionals to address the causes. This includes:

• Airway assessment with an ENT specialist
• Assessment and management of chronic allergies and infections
• Breathing retraining

Targeted dental treatment:
In children we can expand the upper jaw and this can allow the tongue to sit properly on the palate and correct teeth crowding.
In some cases the lower jaw can also be brought forward to improve the airway.
In mouth breathing adults, we can bring the lower jaw forward with a mandibular advancement splint.

How is mouth breathing treated?

Myofunctional therapy for mouth breathing – Myofunctional orofacial therapy is a series of targeted exercises that retrain tongue posture, lip seal and nasal breathing habits. It’s most effective when combined with treating the underlying cause of mouth breathing (allergies, enlarged tonsils, nasal obstruction) rather than used alone.

We recommend myofunctional therapy for:

• Children who continue mouth breathing out of habit even after adenoid or tonsil surgery, or nasal treatment.
• Adults trying to unlearn long-term mouth breathing patterns that contribute to snoring or poor sleep quality.
• Patients undergoing jaw expansion or orthodontic treatment, where correct tongue posture supports better long-term results.

Visit our page Myofunctional Therapy for more information.

Mouth breathing and Sleep apnea

When the mouth stays open during sleep, the tongue tends to fall back into the airway, narrowing it further and making the airway more likely to collapse. In children this can show up as snoring, restless sleep or bedwetting; in adults it’s more often loud snoring, daytime fatigue, or a diagnosed case of obstructive sleep apnoea (OSA).

Because of this link, treating mouth breathing is often part of a broader sleep apnea management plan. Depending on the diagnosis, this may include jaw expansion in growing children, a mandibular advancement splint for adults, or working alongside an ENT and sleep physician for more complex cases.

Can mouth breathing be prevented? 

• Early screening — assessing nasal breathing and airway development from as young as 3-4 years old.
• Prompt treatment of allergies and sinus issues, which are among the most common underlying causes.
• Encouraging nasal breathing habits and myofunctional exercises before they become entrenched.
• Regular check-ups that include airway and tongue posture screening — exactly what we screen for at every 6-monthly visit.

FAQs

Frequently Asked Questions

Can mouth breathing be reversed in adults?

Yes, in many cases. Treating the underlying cause (allergies, nasal obstruction, sleep apnea) combined with myofunctional therapy can retrain nasal breathing habits, though results vary depending on how long the habit has been present.

How do you fix mouth breathing in a child?

Treatment depends on the cause — it may involve allergy management, ENT treatment for enlarged adenoids or tonsils, jaw expansion to widen a narrow palate, and myofunctional therapy to retrain tongue posture and breathing habits.

Is mouth breathing a sign of sleep apnea?

Not always, but it’s a common feature of it. Mouth breathing narrows the airway further during sleep, so if it’s paired with snoring, restless sleep or daytime fatigue, it’s worth having a sleep assessment.

What does myofunctional therapy involve?

A series of guided exercises to retrain tongue posture, lip seal and nasal breathing, usually done over several weeks to months alongside treatment of the underlying cause.

Can mouth breathing cause permanent facial changes?

In children, prolonged mouth breathing during growth years can affect jaw and facial development (sometimes called “adenoid facies”), which is why early screening and treatment matter. In adults, facial growth is complete, but the airway and dental effects can still be treated.

When should I see a dentist or doctor about mouth breathing?

If you notice dry lips, an open-mouth resting posture, snoring, crowded teeth, or a long or narrow facial shape — in yourself or your child — it’s worth a screening. Our 6-monthly check-ups already look for these signs.

Written and reviewed by Dr Roy Kumar — MMBS | FRACGP | DCH | FACNEM | Last review: September 2026

References:

• Zhao, Z. et al. “Effects of mouth breathing on facial skeletal development in children: a systematic review and meta-analysis.” BMC Oral Health, 2021. ncbi.nlm.nih.gov/33691678
• “Mouth Breathing and Craniofacial Development in Children: A Systematic Narrative Review and Clinical Implications.” Healthcare, 2025. ncbi.nlm.nih.gov/articles/PMC13299497
• Lee SY, Guilleminault C, Chiu HY, Sullivan SS. Mouth breathing, “nasal disuse,” and pediatric sleep-disordered breathing. Sleep Breath. 2015 Dec;19(4):1257-64. https://pubmed.ncbi.nlm.nih.gov/25877805/
• “Mouth breathing reduces oral function in adolescence.” Scientific Reports, 2024. com/articles/s41598-024-54328-x
• Suzuki M, Furukawa T, Sugimoto A, Katada K, Kotani R, Yoshizawa T. Relationship between oral flow patterns, nasal obstruction, and respiratory events during sleep. J Clin Sleep Med2015;11(8):855–860. https://pmc.ncbi.nlm.nih.gov/articles/PMC4513262/