What Is Mouth Breathing and Why Does It Matter?

Mouth breathing can develop for a number of reasons. In children, enlarged adenoids or tonsils are among the most common contributors, physically blocking the nasal airway and forcing the child to breathe through the mouth. Chronic allergies, nasal congestion, a deviated septum, and frequent upper respiratory infections can also drive the pattern.

In some cases, the cause is structural — a narrow palate or underdeveloped midface can limit nasal airflow. In others, mouth breathing begins as a temporary response to illness or congestion and becomes habitual even after the original obstruction resolves. The muscles and posture adapt to the open-mouth pattern, and without intervention, the habit persists.

It is also worth noting that many pacifier and thumb-sucking habits encourage an open-mouth posture, which can transition into habitual mouth breathing as the child grows.

In children, chronic mouth breathing can alter the trajectory of facial growth. When the mouth is open at rest, the tongue drops from its natural resting position on the palate and sits low in the mouth. The palate loses the gentle outward pressure from the tongue that helps it develop a wide, U-shaped arch. Over time, the palate narrows, the face elongates, and the lower jaw may recede.

This pattern is sometimes referred to as "long face syndrome" or "adenoid facies." Children who breathe through their mouths often develop a narrow upper jaw, crowded teeth, a gummy smile, and dark circles under the eyes. These are not just cosmetic concerns — they reflect underlying changes in airway development and function.

Mouth breathing during the day almost always means mouth breathing at night. During sleep, mouth breathing contributes to snoring, upper airway resistance, and in some cases, obstructive sleep apnea. When children do not sleep well, the effects show up during the day as hyperactivity, difficulty concentrating, irritability, and behavioral issues that are sometimes misdiagnosed as ADHD.

Adults who mouth breathe at night often experience dry mouth, morning headaches, fatigue, and brain fog. Poor sleep quality from mouth breathing can compound over years, affecting cardiovascular health, immune function, and mental well-being.

Orofacial Myofunctional Therapy (OMT) targets the root muscular and postural patterns that sustain mouth breathing. Therapy focuses on retraining proper tongue resting posture — with the tongue lightly suctioned to the palate — establishing consistent lip seal, and building nasal breathing as the default pattern during the day and night.

For children, early intervention can redirect facial growth toward a healthier pattern and prevent downstream complications. For adults, OMT can improve sleep quality, reduce snoring, support CPAP tolerance, and resolve chronic dry mouth. Therapy is often coordinated with ENTs, allergists, orthodontists, and sleep physicians as part of a comprehensive care plan.

If you or your child habitually breathes through the mouth — whether during the day, while sleeping, or during physical activity — it is worth having it evaluated. Pay attention to whether the lips are apart at rest, whether snoring is present, and whether there are signs of a narrow palate or crowded teeth.

An evaluation with an orofacial myofunctional therapist can identify the contributing factors and determine whether therapy is appropriate. The earlier mouth breathing is addressed, the better the outcomes — but it is never too late to make meaningful improvements.