More Than Just a Habit
When parents notice their child breathing through their mouth, the instinct is often to assume it is temporary. A cold, a bout of hay fever, a phase that will pass. In many cases that is exactly what it is. But in a significant number of children, mouth breathing is not a passing phase — it is a persistent pattern that is quietly and consistently affecting the development of the jaw, the face, the airway, and the quality of every night's sleep.
At Dr Gray Dentistry in Durban, Dr Gray assesses breathing patterns as a routine part of evaluating children's jaw and dental development. Because what happens with the airway during childhood has consequences that extend far beyond the nose and mouth — shaping the face, the bite, and the long-term health of a child in ways that most parents are never told about.
What Is Mouth Breathing?
Mouth breathing is exactly what it sounds like, breathing primarily through the mouth rather than the nose. The nose is the body's designed airway for breathing at rest. It filters, warms, and humidifies incoming air, produces nitric oxide that supports lung function and immune health, and maintains the airway resistance that supports healthy respiratory mechanics.
When a child breathes through their mouth instead, all of these functions are bypassed. But the consequences of mouth breathing extend well beyond air quality because the act of breathing through the mouth, sustained over months and years during the critical growth period of childhood, directly alters the development of the jaw and face in ways that become increasingly difficult to reverse as the child grows.
Signs Your Child May Be a Mouth Breather
Many children who are habitual mouth breathers do so without parents realising the extent of it — because much of the mouth breathing happens during sleep, when the child is not being observed. The following signs are worth watching for:
During sleep
Sleeping with the mouth open consistently
Snoring or noisy breathing during sleep
Restless sleep, frequent position changes, or waking during the night
Drooling on the pillow
Waking unrefreshed despite adequate hours of sleep
Observed pauses or gasping in breathing
During waking hours
The mouth is open at rest, with lips apart rather than gently closed
The child breathes audibly through the mouth during quiet activities
Frequent dry lips or dry mouth
A consistently stuffy or blocked nose that doesn't clear with time
Frequent ear infections, sinus infections, or colds
Nasal speech or a consistently blocked nasal quality to the voice
Facial and dental signs
A long, narrow face developing over time
Dark circles under the eyes
Crowded or protruding front teeth
A high, narrow palate visible when the child opens their mouth
The lower jaw appearing recessed or small
Gummy smile developing as the upper front teeth begin to show more than normal
Behaviour and performance
Daytime sleepiness or fatigue despite what appears to be enough sleep
Difficulty concentrating at school or hyperactive behaviour
Irritability or mood changes that seem disproportionate
A diagnosis or suspected diagnosis of ADHD in a child who also shows sleep and breathing signs
What Causes Mouth Breathing in Children?
Mouth breathing develops when the nasal airway is obstructed, too narrow, or simply less comfortable than breathing through the mouth. The most common causes include:
Enlarged tonsils and adenoids
The tonsils and adenoids are lymphoid tissue that can enlarge significantly during childhood, particularly in response to repeated infection. Enlarged adenoids sit directly behind the nasal passage and can partially or completely obstruct nasal airflow, forcing the child to breathe through the mouth. This is one of the most common and most correctable causes of childhood mouth breathing, and referral to an ENT specialist for assessment of tonsil and adenoid size is a logical early step when mouth breathing is identified.
Allergic rhinitis
Chronic nasal congestion from allergies to dust mites, pollen, animal dander, or mould is a very common cause of habitual mouth breathing. The congested nasal passages make nasal breathing uncomfortable or impossible, and the child defaults to mouth breathing as the path of least resistance. Managing the underlying allergy often produces significant improvement in breathing pattern.
A narrow nasal passage
Some children have structurally narrow nasal passages that make nasal breathing more effortful even in the absence of inflammation or obstruction. This structural narrowness is frequently related to a narrow upper jaw and is one of the reasons that palatal expansion, which widens the upper jaw and simultaneously widens the nasal floor above it, can produce meaningful improvement in nasal breathing.
Habitual mouth breathing
In some children, mouth breathing that began as a response to a temporary obstruction becomes a habit that persists even after the original obstruction has resolved. The child has simply learned to breathe through the mouth and continues to do so even when nasal breathing is technically available. Breaking this habit typically requires conscious retraining.
How Mouth Breathing Affects Jaw and Facial Development
This is the aspect of mouth breathing that is most important for parents to understand and most consistently overlooked in general healthcare settings.
The tongue's role in jaw development
When a child breathes nasally, the tongue rests in its correct position against the roof of the mouth, the palate. This tongue pressure against the palate is not incidental. It is a developmental force that actively shapes the upper jaw as it grows, encouraging the palate to be wide, flat, and well-formed to accommodate all the permanent teeth.
When a child breathes through the mouth, the tongue drops to the floor of the mouth to allow airflow. The developmental pressure against the palate is lost. Without this pressure, the upper jaw grows narrow and high-arched rather than broad and flat. A narrow upper jaw means less room for the permanent teeth, more crowding, a narrower nasal floor above the palate, and a bite that is increasingly difficult to manage.
Forward head posture
Mouth breathing is consistently associated with forward head posture, where the head sits in front of the shoulders rather than directly above them. The child instinctively extends the neck and drops the lower jaw to open the airway, and this posture becomes habitual. Forward head posture affects not just the neck and upper back but the position of the jaw, contributing to the TMJ strain discussed in detail in the TMJ section of this content library.
The adenoid face
Children who have been mouth breathing for an extended period often develop what is classically described as an adenoid face: a long, narrow face with a small chin, crowded teeth, a high-arched palate, dark circles under the eyes, and a consistently open-mouthed expression. This facial pattern develops because the absence of normal nasal breathing and tongue posture removes the developmental pressures that normally shape the face, allowing gravity and muscle imbalance to drive facial growth in a less favourable direction.
The Sleep Connection
Mouth breathing and disrupted sleep are closely linked in children, and the consequences of poor sleep in childhood are significantly more serious than in adults. A child's brain and body are actively developing, and the quality of sleep during the growth years directly affects cognitive development, emotional regulation, immune function, and physical growth.
Children who are mouth breathing at night frequently experience fragmented, unrestorative sleep. They may cycle through lighter sleep stages more often, experience brief arousals that they don't remember but that prevent deep restorative sleep from occurring, and sometimes experience episodes of obstructive sleep apnoea where the airway partially or fully collapses during sleep.
The behavioural consequences of this sleep disruption are well documented but frequently misattributed. A child who is chronically sleep-deprived from airway-related sleep disturbance does not typically look tired in the way an adult does. Instead they may present as hyperactive, inattentive, impulsive, and emotionally dysregulated, a pattern that overlaps significantly with ADHD and is frequently mistaken for it. Before a diagnosis of ADHD is accepted in a child who also shows signs of mouth breathing and disrupted sleep, assessment of the airway is strongly advisable.
What Can Be Done?
The good news is that mouth breathing in children is addressable, and the earlier it is identified and managed, the better the outcome for jaw development, facial growth, and sleep quality.
Identify and treat the underlying cause
The first step is understanding why the child is mouth breathing. Enlarged tonsils and adenoids, allergic rhinitis, and structural nasal narrowing are all identifiable and treatable. Dr Gray may refer to an ENT specialist, allergist, or GP depending on the suspected cause.
Palatal expansion
Where a narrow upper jaw is contributing to nasal airway restriction, palatal expansion widens the upper arch and simultaneously increases the volume of the nasal passage above it, creating more room for nasal airflow. This is one of the most impactful early orthodontic interventions available for mouth-breathing children and is discussed in detail in the palatal expander post in this series.
Myofunctional therapy
Myofunctional therapy involves exercises that retrain the tongue, lip, and breathing muscles to adopt correct resting postures and nasal breathing patterns. It is particularly valuable for children whose mouth breathing has become habitual and for whom structural causes have already been addressed.
Nasal breathing retraining
Simple, consistent encouragement of nasal breathing during waking hours, combined with nasal hygiene measures such as saline rinses to reduce congestion, can support the transition back to nasal breathing in children whose obstruction has been resolved.
When to Seek Assessment
If your child consistently sleeps with their mouth open, snores, seems chronically tired despite adequate sleep, or has the dental and facial signs described in this post, an assessment that considers both the airway and the jaw is the appropriate next step.
Dr Gray at Dr Gray Dentistry in Durban, South Africa assesses breathing patterns, jaw development, and palatal width as part of a comprehensive early orthodontic evaluation, and works with a network of ENT specialists, GPs, and other practitioners to ensure the full picture is addressed rather than just the dental component in isolation.
Book your child's assessment at Dr Gray Dentistry in Durban today.