Mouth breathing is a hot topic discussed on social media and among parenting groups. Parents should be aware that there is a lot of misinformation and weak research evidence in this area (especially for children). That being said, there is some support for mouth breathing having an impact on your child’s teeth so lets get into it!

What is mouth breathing?

Mouth breathing occurs when you breathe more through your mouth than your nose. A rule of thumb (not a diagnosis) is over 25-30% of breathing through your mouth qualifies as mouth breathing.

Mouth breathing is often discussed under a broader diagnosis known as Obstructive Sleep Apnea. Mouth breathing alone is not a formal disorder or diagnosis, unlike Obstructive Sleep Apnea. This post will be focusing on mouth breathing.

Mouth breathing occurs because nasal breathing is impaired. Breathing should ideally be through the nasal passages: this is necessary for proper facial development.

Are there any methods to confirm mouth breathing?

Mouth breathing does not have a consistent diagnostic criteria. Below are a few simple methods to see if someone is mouth breathing:

• Lip Seal test: seal the lips and see if they can breathe through their nose comfortably for an extended period of time. If there is difficulty, then there may be a dependence on mouth breathing.
• Water Test: Have your child hold water in their mouth and ask them to breathe through their nose. Mouth breathers will not be able to hold the water in their mouth for long.
• Mirror Test: Hold a mirror or metal spoon under your child’s nose or mouth while they breathe. If you see fog on the mirror, then they are breathing adequately through the respective passageway.

What are the causes and treatments for impaired nasal breathing?

Mouth breathing is caused by a blockage or impairment in the nose reducing airflow. Contributing factors include obesity, poor sleeping positions and environmental irritants.

Nose breathing can be impaired for multiple reasons stated below:

1) Large Adenoids/Tonsils

This is the #1 reason for mouth breathing in kids! These soft tissues take up a lot of space and reduce the size of the airway.

Adenoids grow from 2-5 years old and decrease in size after 10 years old. Tonsils grow from 2-6 years old and decrease in size by 14-15 years. This means that most mouth breathing disappears with age.

Large adenoids/tonsils alone does not mean you will always have mouth breathing! There is no formal cutoff point where tonsils are “too big” and will absolutely cause breathing problems.

Treatment for large adenoids or tonsils is surgical removal by a surgeon. Sometimes breathing can still be impaired after removal as the tissues may grow back over time.

2) Enlarged Turbinates or Deviated Septum

Turbinates are structures in your nose that moisten and clean the air. Allergies, infections and irritation can cause swelling and make it hard for you to breathe through your nose.

Deviated Septum: The septum is the cartilage and bone that divides your nose. If it is too close to one side, it could reduce airflow in your nose.

Treatment for these causes involve surgical correction with a head and neck/ENT surgeon. If there are irritants causing swelling or enlargement, then these can be managed with medications.

3) Nasal Congestion

Chronic stuffy nose can impair nasal airflow. Contributing factors could be allergies, viral illnesses, pollution or smoke exposure. Your physician should be seen if your child is having chronic congestion.

Treatments can include antihistamines, steroid sprays, decongestants and antibiotics if your child has chronic congestion. You can also try removing irritants (smoke, animals, pollen etc.) from your child’s environment. Nasal blockage in these cases may be temporary or seasonal.

4) Nasal polyps

These are growths that can occur in your nose and result in a blockage. Treatment for these is surgical removal if the polyps are very large and cause problems.

What are some symptoms of mouth breathing?

Symptoms of significant mouth breathing can include the following:

• Dry mouth
• Bad breath
• Snoring
• Daytime Tiredness
• Drooling when asleep

What is the connection between mouth breathing and teeth?

Mouth breathing and dental changes are often seen on social media. This connection is not strong based on current research and there is lots of misinformation online. Facial and dental development is influenced by genetics, habits, environments and other factors.

Mouth breathing alone has not been proven to cause dental changes. At most, mouth breathing can be associated with bite problems. This means the 2 traits (mouth breathing and bite problems) are seen together sometimes. This is not enough to say mouth breathing will cause bite changes.

For example, smoking and lung cancer are not associated: smoking is proven to cause cancer. Smoking and cancer do not occur together by chance. However, patients that mouth breathe don’t all have bite problems and the majority of patients with crowding or bite issues breathe normally.

Mouth breathing or enlarged tonsils/adenoids alone does not mean your child will have dental or facial problems. Don’t forget majority of mouth breathing disappears with age as adenoids/tonsils shrink

Mouth breathing is difficult to diagnose in studies. Nasal and mouth breathing are also difficult to separate when assessing them for research. Humans rarely only breathe through their mouth. The duration of mouth breathing is also a variable that cannot be measured easily: A child breathing for 2 years verses 10 years through their mouth would have different changes.

Does expanding my child’s upper jaw prevent or treat mouth breathing?

A dental option to increase the size of the nasal airway is to expand the upper jaw with a palatal expander appliance. This should be provided by an orthodontist. However, current evidence supporting this is weak. The American Journal of Orthodontics reports potential harms when expansion is performed solely for mouth breathing without signs of bite problems.

The American Association of Orthodontists states there is no evidence to support early palatal expansion to solely prevent breathing disorders.

Your child ideally should be cleared of any other nasal impairments before doing upper jaw expansion solely for mouth breathing. A thorough discussion should occur to understand risks and benefits.

What is “mouth breathing face”?

“Mouth breathing face” (also called adenoid facies) is a set of traits that are supposedly caused by extensive mouth breathing. The evidence to support this is very poor but lets discuss it since commonly seen online.

Mouth breathing changes positioning of the head, lower jaw and tongue. The head is tipped back and lower jaw and tongue are lowered. This can cause a muscular imbalance on the jaws/teeth.

The tongue puts less pressure on the palate and upper teeth. The cheeks/lips press on the teeth and this can cause upper jaw narrowing. The lower jaw rotates back and has a steeper angle. The lips cannot touch with this jaw position. Crowded teeth result from the changes the in the jaw sizes.

The facial changes also include a long facial height, narrow upper jaw, retruded lower jaw, lip incompetence (lips cannot touch), steeper and posterior-rotated lower jaw.

Can mouth breathing cause cavities or gum disease?

Some studies claim that mouth breathing can increase risk of cavities and gum disease. This is another area of questionable evidence as there are many confounding variables.

Mouth breathing theoretically can cause your saliva to dry up. Saliva prevents cavities by washing away sugar and neutralizing acid. Less saliva in the mouth can technically cause dry-mouth which would increase risk of gingivitis and cavities. That being said, this is an area that needs further research and these associations should be taken with a grain of salt.

The primary cause of cavities and gum disease is diet and oral hygiene.

Does mouth breathing cause ADHD?

This is not proven. Attention Deficit Hyperactivity Disorder (ADHD) is complex neurodevelopmental disorder characterized by hyperactivity, inattention and impulsivity. The causes are wide-ranging from prenatal factors, environmental toxins, psycho-social factors among others.

While poor sleep can contribute to restlessness and inattention, this is not equivalent to causing ADHD. Claims suggesting otherwise are misleading.

Who should I first see if I am concerned about mouth breathing in my child?

Start with your physician.

The causes of mouth breathing are based on the obstruction in the nasal passages. The #1 cause of mouth breathing in kids is large adenoids and tonsils. Other causes can be treated medically as stated above.

There should also be an assessment of any inattentiveness, daytime sleepiness or developmental delays before providing a diagnosis or treatment. These are all in the scope of medical practitioners.

Constant mouth breathing may be a symptom of deeper problems such as Obstructive Sleep Apnea, which would warrant medical consult.

Your dentist and other health care professionals play an important supporting role and can work with your medical providers to address the specific dental concerns. Dentists should not lead treatment of breathing disorders without medical involvement.

So what role does my dentist play in my child’s mouth breathing?

The American Academy of Pediatric Dentistry and the American Association of Orthodontists recommend dentists should refer to a medical professional first if they suspect breathing issues! There are dental options for mouth breathing but it is not the first go-to treatment usually.

Dentists have a role with other professionals managing the dental-specific concerns of mouth breathing. They can work in a multi-disciplinary approach to provide your child’s care. Upper jaw expansion alone may not be the right option for treating breathing concerns.

Dentists can be involved with screening for sleep-disordered breathing and assessing dental factors in breathing disorders. We can help in prevention and treatment of cavities and periodontal disease. Your orthodontist can address any bite or facial changes.

The final word…

Mouth breathing is common and caused by obstruction in the nasal airway. There is an association (not causation) with dental changes. Overall, this is a heavily debated area with weak support. Parents should begin with their medical providers to be thoroughly assessed. Dentists play a valuable role in managing dental effects and coordinating care but they are not the primary providers for breathing disorders.

References:

American Academy of Pediatric Dentistry. Policy On Obstructive Sleep Apnea (OSA). The Reference Manual of Pediatric Dentistry. Chicago, IL: American Academy of Pediatric Dentistry; 2025:145-8.

Behrents RG, Shelgikar AV, Conley RS, Flores-Mir C, Hans M, Levine M, McNamara JA, Palomo JM, Pliska B, Stockstill JW, Wise J, Murphy S, Nagel NJ, Hittner J. Obstructive sleep apnea and orthodontics: An American Association of Orthodontists White Paper. Am J Orthod Dentofacial Orthop. 2019 Jul;156(1):13-28.e1. doi: 10.1016/j.ajodo.2019.04.009. PMID: 31256826.

Becking BE, Verweij JP, Kalf-Scholte SM, Valkenburg C, Bakker EWP, van Merkesteyn JPR. Impact of adenotonsillectomy on the dentofacial development of obstructed children: a systematic review and meta-analysis. Eur J Orthod. 2017 Oct 1;39(5):509-518. doi: 10.1093/ejo/cjx005. PMID: 28379334.

Cleveland Clinic. Mouth Breathing: Symptoms, Complications & Treatment (2025). https://my.clevelandclinic.org/health/diseases/22734-mouth-breathing

Festa P, Mansi N, Varricchio AM, Savoia F, Calì C, Marraudino C, De Vincentiis GC, Galeotti A. Association between upper airway obstruction and malocclusion in mouth-breathing children. Acta Otorhinolaryngol Ital. 2021 Oct;41(5):436-442. doi: 10.14639/0392-100X-N1225. PMID: 34734579; PMCID: PMC8569668.

Kandasamy S. Mouth breathing and orthodontic intervention: Does the evidence support keeping our mouths shut? Am J Orthod Dentofacial Orthop. 2025 Jun;167(6):629-634. doi: 10.1016/j.ajodo.2025.02.005. Epub 2025 Mar 6. PMID: 40057896.

Lin L, Zhao T, Qin D, Hua F, He H. The impact of mouth breathing on dentofacial development: A concise review. Front Public Health. 2022 Sep 8;10:929165. doi: 10.3389/fpubh.2022.929165. PMID: 36159237; PMCID: PMC9498581.

Ma Y, Xie L, Wu W. The effects of adenoid hypertrophy and oral breathing on maxillofacial development: a review of the literature. J Clin Pediatr Dent. 2024 Jan;48(1):1-6. doi: 10.22514/jocpd.2024.001. Epub 2024 Jan 3. PMID: 38239150.

do Nascimento RR, Masterson D, Trindade Mattos C, de Vasconcellos Vilella O. Facial growth direction after surgical intervention to relieve mouth breathing: a systematic review and meta-analysis. J Orofac Orthop. 2018 Nov;79(6):412-426. English. doi: 10.1007/s00056-018-0155-z. Epub 2018 Sep 19. PMID: 30232505.