Mouth Breathing: Causes and Consequences

Mouth breathing is an abnormal way of breathing. It's a very common disorder among the general population with serious long-term results. Let's see why it happens and its consequences.
Mouth Breathing: Causes and Consequences
Leonardo Biolatto

Written and verified by the doctor Leonardo Biolatto.

Last update: 27 May, 2022

Mouth breathing isn’t the normal way of breathing. As humans, our nose is a specialized organ to inhale and expel air from and to our body. When we breathe through the mouth it’s because something is happening that alters the normal development of breathing. It may be an obstruction in the airway or an acquired bad habit.

When mouth breathing is perpetuated over time, becoming chronic, the consequences could be worse and worse. The greater the exposure to air inhaled through the mouth, the greater the problems in the future. Therefore, it’s more difficult to treat.

We have to understand that the nose has essential functions in breathing. Because of its anatomical arrangement, it’s responsible for humidifying the air that enters the body. Nasal mucosa makes inspiration more efficient by protecting the internal organs. The nose is also a filter for bacteria and particles that may enter from the outside. Contaminating elements are stopped by the nasal anatomy, preventing allergies and infections.

Symptoms of mouth breathing

It might seem that mouth breathing is a fairly obvious issue. By just seeing that a person opens their lips to bring air into the body, we could already have the diagnosis. Unfortunately, the issue isn’t that simple.

Mouth breathing can be momentary, and even physiological. In situations of high oxygen requirements, human physiology resorts to the mouth. What isn’t normal is that this should persist over time.

Among the symptoms of mouth breathing, we can list the following:

  • Presence of the tongue between the teeth when closing the oral cavity.
  • Poor night’s rest: tiredness and exhaustion during the day, in addition to signs of poor sleep, such as dark circles under the eyes.
  • Altered timbre voice: children may speak with a slurred voice, or with a so-called nasal voice, which doesn’t sound normal.
  • Dental alterations: mouth-breathing alters children’s dental arches. The teeth are poorly positioned and the appearance of teeth may even be delayed.
  • Dryness: both the buccal mucosa and the lips become dry when breathing through the mouth. It’s common for cracks to appear at the corners of the mouth.
  • Repeated infections: mouth breathers suffer from repeated pharyngitis, sinusitis and otitis. Poor respiratory dynamics eliminates the first barrier for microorganisms, which enter at ease.
  • Snoring: when sleeping, the mouth breather snores, and this leads to sleep apneas, which consist of small nocturnal awakenings that the person doesn’t notice.
A graphic of human breathing.

Also read: Four Alternative Treatments to Control Snoring

Causes of mouth breathing

In general, obstructed airways force our body to breathe through the mouth. The causes of obstruction are varied, among them:

  • Tonsillar hypertrophy is a common condition in the pediatric age group. The lymphatic tissue of the tonsils or adenoids -or both- is enlarged. Due to their position, when the tonsils become enlarged, part of the air passage through the nose is interrupted.
  • Rhinitis and sinusitis: Chronic inflammation of the nasal mucosa or sinuses obviously complicates nasal breathing. It may be a continuous allergic reaction or repeated infections. Whatever the origin, the end result tends to be the same, with difficulty for air to enter through the nose.
  • Septal deviation: Due to birth defects or trauma, the septum of the nose may deviate. If the deviation is significant, either or both nostrils have a blockage at the same time. Although corrective surgery is available for a deviated septum, sometimes symptoms persist even after surgery.
  • Nasal polyps: The mucosa of the nose can overgrow into the lumen of the nostrils. These abnormal growths are nasal polyps. Either by quantity or volume, they tend to obstruct airflow.
A man snoring.


In conclusion, there are serious consequences when mouth breathing for long periods. It’s very difficult to achieve a reversal of the changes that occur. Among these consequences, we can name the following:

  • Respiratory infections: from colds to pneumonia.
  • Lack of cerebral oxygenation: the air inhaled through the mouth decreases the use of oxygen. Less oxygen circulating depresses neuronal functions. Learning deficits are common in mouth-breathing children.
  • Alterations of the spine: mouth breathing is associated with poor general body posture. The mouth breather brings their head forward and the spine copies this movement by changing its structure.
  • Poor development of the skull: nasal breathing has among its indirect functions that of molding the bones of the head during growth. If the child breathes through the mouth from an early age, this doesn’t stimulate the bones of the skull properly. The lower jaw doesn’t enlarge sufficiently and the palate becomes ogival, like a thin dome upwards.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • López, Juan Hernández, and René Pablo Céspedes Isasi. “Respiración bucal. Nivel de conocimientos de padres o tutores.” MULTIMED 23.3 (2019).
  • Marchesan, Irene Queiroz. “Evaluación y terapia de los problemas de respiración.” Centro de Especialização em Fonoaudiologia Clínica. (2016).
  • García Triana, Bárbara Elena, Ahlam Hibatulla Ali, and Ileana Bárbara Grau León. “Respiración bucal y su relación con algunas afecciones bucales y médicas: mecanismos fisiopatológicos involucrados.” Revista Habanera de Ciencias Médicas 15.2 (2016): 200-212.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.