Mouth breathing, or oral respiration, is the act of inhaling and exhaling primarily through the mouth instead of the nose. While occasional mouth breathing is normal during temporary conditions like a severe cold, chronic oral respiration signals an underlying airway issue. The habit itself is not genetic, but the structural and physical factors that force a person to breathe this way can be inherited or acquired. Understanding the specific causes and resulting health impacts is the first step toward promoting nasal breathing.
Understanding Non-Hereditary Causes
The majority of chronic mouth breathing cases result from physical, non-inherited obstructions in the nasal passage. The nose is the body’s natural air filter and humidifier, and when its function is impaired, the mouth takes over. This shift is often triggered by temporary or acquired conditions that physically block airflow.
One of the most frequent causes is chronic nasal congestion due to seasonal or year-round allergies, medically termed rhinitis. When the nasal passages become inflamed and swollen, the air pathway narrows, necessitating oral breathing for adequate oxygen intake. Acute respiratory infections, such as the common cold or flu, also cause temporary nasal blockage, though this pattern usually reverts to normal after recovery.
In children, a common physical barrier is enlarged adenoids or tonsils, which are lymphoid tissues located at the back of the throat and nasal cavity. When these tissues become enlarged, they can partially or completely obstruct the upper airway, forcing the child to breathe through their mouth. Nasal polyps, which are soft, non-cancerous growths on the lining of the nasal passages or sinuses, also physically impede airflow. These acquired causes establish the habit of oral breathing, even if the initial obstruction later resolves.
Inherited Anatomical Predispositions
While the behavior of mouth breathing is acquired, certain inherited anatomical structures can create a predisposition for it. Genetic factors influence the size and shape of the craniofacial complex, which includes the bones of the face and skull. Individuals can inherit a naturally narrow structure of the nasal passages or the overall airway, making nasal breathing difficult even without inflammation.
The development of the jaws is also subject to genetic influence, with certain traits predisposing a person to breathing issues. For instance, a genetically smaller maxilla (upper jaw) can result in a high, narrow palate that crowds the nasal cavity floor, reducing space for airflow. Similarly, retrognathia, a condition involving a receded lower jaw, can indirectly compromise the airway and encourage an open-mouth posture. These inherited structural features do not cause mouth breathing directly, but they create a mechanical environment where the habit is more likely to develop.
Health Consequences of Chronic Breathing Patterns
Prolonged oral respiration has far-reaching effects because it disrupts the normal balance of the oral and respiratory systems. One of the most noticeable impacts is on craniofacial development, particularly in growing children. When the mouth is consistently open, the tongue rests low instead of against the palate, which is necessary to support the natural, outward growth of the upper jaw.
This lack of supportive pressure from the tongue leads to a narrow upper dental arch and a high-arched palate, often resulting in dental malocclusion, such as crowded teeth or an overbite. The characteristic facial changes associated with this, sometimes termed “adenoid facies,” include an elongated face and a receding chin. Chronic mouth breathing also compromises dental health by causing constant dry mouth, as the protective effects of saliva are reduced. This dryness increases the acidity, creating an environment highly susceptible to tooth decay, gingivitis, and bad breath.
On a systemic level, the habit is linked to poor sleep quality and fatigue, as it can contribute to or exacerbate sleep disordered breathing and obstructive sleep apnea. The body also bypasses the nose’s natural filtering and warming functions, allowing unfiltered, dry air to reach the lungs. This increases the risk of respiratory irritation and infection. This cycle of poor sleep and reduced air quality can impact concentration and overall daytime function.
Pathways for Correction and Treatment
Addressing chronic mouth breathing requires a multidisciplinary approach focused on eliminating the underlying cause and retraining the breathing pattern. A medical evaluation often begins with an otolaryngologist (ENT specialist) who identifies physical obstructions in the airway. Treatments can include medication to manage allergies and reduce chronic inflammation, or surgical intervention like tonsillectomy, adenoidectomy, or septoplasty to remove blockages.
Orthodontic treatment plays a role, especially when structural changes have occurred. For growing patients, palatal expansion devices may be used to widen the narrow upper jaw, increasing space in the nasal cavity and making nasal breathing easier. Once physical and structural impediments are addressed, behavioral retraining is often necessary to break the established habit.
Myofunctional therapy is a specialized form of physical therapy that uses targeted exercises to strengthen the tongue and facial muscles. This therapy focuses on achieving proper oral rest posture: lips sealed and the tongue resting against the roof of the mouth. This encourages the transition back to nasal breathing. By combining medical intervention, structural correction, and behavioral retraining, individuals can successfully correct chronic oral respiration.