Newborns are considered obligate nose breathers, meaning their anatomy is designed so that breathing happens almost exclusively through the nose during the first several months of life. If your newborn regularly breathes through the mouth, something is likely interfering with normal nasal airflow, and it deserves attention. The causes range from simple congestion to rare structural abnormalities, and the urgency depends on how much it affects your baby’s breathing, feeding, and sleep.
Why Newborns Are Meant to Breathe Through the Nose
Unlike older children and adults who can easily switch between nose and mouth breathing, newborns have an airway structure that strongly favors the nasal route. The soft palate sits high and close to the epiglottis, creating a nearly sealed channel from nose to lungs. This arrangement lets babies breathe and swallow simultaneously during feeding, which is critical for breastfeeding or bottle-feeding without choking. When nasal passages are blocked and a baby is forced to breathe through the mouth, the consequences go beyond simple discomfort. Research in both human neonates and animal models has shown that the effects of forced oral breathing are “pervasive and profound, and sometimes last into adulthood.”1PubMed Central. It takes a mouth to eat and a nose to breathe: abnormal oral respiration affects neonates’ oral competence and systemic adaptation
The nose does far more than just let air in. The nasal passages warm and humidify incoming air before it reaches the lungs, and the curved structures inside the nose filter out particles and pathogens. The paranasal sinuses also produce nitric oxide, a gas that travels into the lungs during nasal breathing and helps open blood vessels in the lung tissue. Studies in healthy subjects have confirmed that blood oxygen levels rise during nasal breathing compared to oral breathing, thanks in part to this nitric oxide effect.2PubMed. Inhalation of nasally derived nitric oxide modulates pulmonary function in humans For a newborn whose lungs are still maturing, that boost matters.
The Most Common Reasons a Newborn Breathes Through the Mouth
Before worrying about rare conditions, it helps to know that the vast majority of nasal obstruction in newborns comes from ordinary causes. A review in the pediatric literature found that most cases are due to neonatal rhinitis, viral upper respiratory infections, and sometimes reactions to milk or soy proteins.3Minerva Pediatrica. Nasal obstruction in neonates and infants Newborn nasal passages are tiny, and even a small amount of mucus or swelling can make nose breathing difficult. You might notice your baby snorting, sounding congested, or opening the mouth to breathe, especially during feeding or sleep.
Common culprits include:
- Mucus buildup: Newborns produce mucus but cannot blow their noses. Dried or thick mucus in the narrow nasal passages can partially block airflow.
- Viral colds: Even a mild upper respiratory infection causes enough swelling in a newborn’s nose to force mouth breathing.
- Dry air: Low humidity in the home, particularly during winter or in air-conditioned rooms, dries out nasal passages and thickens mucus.
- Milk or formula reflux: Small amounts of milk that travel back up through the nasal passages can irritate and swell the lining.
These causes are temporary and manageable. But if your baby’s mouth breathing is persistent, present from birth, or accompanied by obvious distress, a structural cause needs to be ruled out.
Structural Problems That Block a Newborn’s Nose
A small number of newborns are born with anatomical abnormalities that physically obstruct the nasal airway. These tend to show up immediately or within the first days of life, and they often cause more dramatic symptoms than simple congestion.
Choanal atresia is the most well-known structural cause. In this condition, the back of one or both nasal passages is blocked by bone or soft tissue, preventing air from flowing through the nose into the throat. When both sides are blocked (bilateral choanal atresia), it creates a respiratory emergency at birth because the baby cannot breathe through the nose at all. Babies with bilateral choanal atresia typically turn blue (become cyanotic) when their mouth is closed and improve when they cry, since crying forces mouth breathing. This pattern is so distinctive that it often leads to rapid diagnosis in the delivery room.4PubMed Central. Practical Tips for Surgical Management of Bilateral Choanal Atresia
When only one side is blocked (unilateral choanal atresia), the symptoms are subtler. The baby can still breathe through the open side, so the condition might not be noticed until congestion from a cold tips the balance and the baby suddenly struggles. Unilateral cases sometimes go undetected for months or even years.
Congenital nasal pyriform aperture stenosis is another rare structural cause. The bony opening at the front of the nasal cavity is abnormally narrow because of overgrowth of the maxillary bone. Because it is so uncommon, it is frequently missed.5PubMed Central. Nasal Pyriform Aperture Stenosis in a Newborn: When to Operate Babies with this condition present similarly to those with choanal atresia, with noisy breathing, feeding difficulty, and episodes of distress when both nostrils are obstructed.
Other airway abnormalities can also contribute to breathing trouble in infancy, including laryngomalacia (a floppy larynx that collapses inward during breathing), hemangiomas (benign vascular growths in the airway), and laryngeal webs. Each of these can compromise airway patency and contribute to obstructive symptoms.6PubMed Central. Obstructive sleep apnea in infants
How Mouth Breathing Disrupts Feeding
Feeding is where mouth breathing creates the most immediate practical problem for new parents. Breastfeeding and bottle-feeding both require a baby to coordinate sucking, swallowing, and breathing in a rapid rhythm. Healthy term infants typically suck a few times, swallow, and then take a breath, cycling through this pattern dozens of times per minute. During active feeding, the ratio shifts so that more sucks happen per swallow as milk flow changes.7PubMed Central. Oxygen Saturation and Suck-Swallow-Breathe Coordination of Term Infants during Breastfeeding and Feeding from a Teat Releasing Milk Only with Vacuum
When the nose is blocked, this coordination falls apart. The baby has to release the breast or bottle to gasp for air through the mouth, breaking the feeding rhythm. You might notice your baby pulling off the breast frequently, making clicking sounds, swallowing air (which leads to more gas and fussiness), or simply refusing to feed for more than a few seconds at a time. Over days and weeks, poor feeding efficiency can slow weight gain. In severe cases where airway obstruction persists, failure to thrive becomes a genuine concern.
Sleep, Oxygen, and Safety Risks
Mouth breathing during sleep is particularly concerning in infants. Newborns spend most of their time asleep, and during sleep the muscles that hold the airway open relax. Infants are already predisposed to airway obstruction during sleep because of their anatomy, including a high larynx and a very compliant (soft, flexible) chest wall. When nasal obstruction is layered on top of these normal vulnerabilities, the risk of obstructive sleep apnea increases.
Obstructive sleep apnea in infants has been linked to failure to thrive, behavioral deficits, and sudden infant death.6PubMed Central. Obstructive sleep apnea in infants Signs that your baby may be experiencing obstructive episodes during sleep include audible snoring (unusual in healthy newborns), pauses in breathing followed by gasps or startles, restless sleep with frequent arousals, and unusual sleeping positions such as hyperextending the neck to open the airway.
If you notice your baby consistently breathing through the mouth during sleep and any of these additional signs, bring it to your pediatrician’s attention promptly. These are not behaviors to monitor at home for weeks hoping they resolve.
What Happens When Mouth Breathing Becomes Chronic
For babies whose mouth breathing persists beyond infancy and into early childhood, the developmental consequences extend to the bones and soft tissues of the face. A child who breathes through the mouth tends to hold the jaw open and the tongue low, rather than resting the tongue against the roof of the mouth. Over months and years of growth, this altered posture reshapes the developing facial skeleton.
A systematic review and meta-analysis comparing mouth-breathing children to nasal-breathing children found consistent differences in facial structure. Mouth-breathing children had a longer, narrower face with a steeper jaw angle and a more recessed midface and chin. The airway behind the tongue and soft palate was also narrower in the mouth-breathing group.8PubMed Central. Effects of mouth breathing on facial skeletal development in children: a systematic review and meta-analysis This pattern is sometimes called “long face syndrome” or “adenoid facies,” and it goes hand-in-hand with dental problems: narrow palates, crowded teeth, open bites, and malocclusion.9Romanian Journal of Oral Rehabilitation. MOUTH BREATHING AND ITS IMPACT ON ORTHODONTIC TREATMENT AND OROFACIAL DEVELOPMENT: A SYSTEMATIC REVIEW
The reason this matters for newborns is timing. The earlier chronic mouth breathing begins, the longer it has to influence craniofacial growth. Addressing the underlying cause of nasal obstruction in infancy, whether that is enlarged adenoids, chronic allergies, or a structural narrowing, can prevent or limit these skeletal changes. Waiting until a child is school-aged and the facial changes are already established makes correction harder and often requires orthodontic treatment.
What You Can Safely Do at Home
For temporary, congestion-related mouth breathing, several home measures can help your baby breathe more easily through the nose:
- Saline drops: A few drops of plain saline (salt water) solution in each nostril loosens dried mucus and reduces mild swelling. This is safe for newborns and can be used before feedings and sleep. Use saline made specifically for infants, available at any pharmacy.
- Gentle suction: After saline drops have had a moment to work, use a bulb syringe or a parent-operated nasal aspirator to gently clear mucus. Be gentle; overly aggressive suctioning can irritate and swell the lining, making things worse.
- Humidifier: Running a cool-mist humidifier in your baby’s room keeps the air moist, which prevents nasal mucus from drying out and thickening. Clean the humidifier regularly to avoid mold growth.
- Upright positioning after feeds: Holding your baby upright for 15 to 20 minutes after feeding reduces the chance of milk refluxing into the nasal passages.
These interventions address the symptoms. If they work and your baby’s nose breathing improves, the cause was likely simple congestion. If they don’t help after a few days, or if the mouth breathing has been present since birth and never lets up, something more than mucus is going on.
What You Should Not Do
The internet is full of well-intentioned advice for congested babies, and some of it is genuinely dangerous for newborns.
Mouth taping has gained popularity on social media as a supposed fix for mouth breathing in adults and children. A systematic review of mouth taping for sleep-disordered breathing found that it is explicitly not recommended for patients with moderate or severe obstructive sleep apnea because it can impose dangers rather than benefits.10PubMed Central. Breaking social media fads and uncovering the safety and efficacy of mouth taping in patients with mouth breathing, sleep disordered breathing, or obstructive sleep apnea: A systematic review For a newborn who may already have compromised nasal breathing, taping the mouth closed could be catastrophic. There is no scenario in which mouth taping is appropriate for an infant.
Over-the-counter cough and cold medications are another hazard. The FDA does not recommend cough and cold products containing antihistamines or decongestants for children under two years old.11PubMed Central. The Use and Safety of Cough and Cold Medications in the Pediatric Population These medications lack evidence of benefit in young children and carry risks of serious adverse effects, including sedation, abnormal heart rhythms, and in extreme cases, death. Even “natural” or herbal remedies marketed for infant congestion should be discussed with a pediatrician before use. Stick with saline and suction for newborns.
Menthol rubs, essential oils applied near the face, and vapor products designed for older children should also be avoided in newborns. They can irritate delicate mucous membranes and, in the case of camphor-containing products, pose a toxicity risk if ingested.
How Doctors Evaluate a Newborn’s Nasal Obstruction
When mouth breathing is persistent or severe enough to affect feeding, sleep, or weight gain, your pediatrician will want to investigate. The evaluation usually starts simply. A careful history covering when the symptoms started, whether they are constant or come and go, and how feeding is going gives the doctor important clues. If symptoms have been present since birth and never improve, a structural cause is more likely. If they started after a few weeks and fluctuate, infection or allergy is higher on the list.
The physical exam includes looking at the nose for obvious deformities, checking whether air flows through each nostril (sometimes done by holding a wisp of cotton or a cold mirror under the nose), and examining the mouth and throat. If the initial exam suggests an anatomical problem, the next step is often nasal endoscopy, a thin flexible scope passed through the nostril to visualize the entire nasal passage and the back of the nose. Imaging studies such as CT scans are added when anatomical obstructions or associated anomalies need to be mapped before treatment.12PubMed Central. Neonatal Nasal Obstruction: A Comprehensive Analysis of Our 20 Years’ Experience
For babies who show signs of sleep-disordered breathing, a sleep study (polysomnography) may be recommended. This is the gold standard for diagnosing obstructive sleep apnea in infants, though it requires specialized pediatric sleep labs and can be logistically challenging with a very young baby.
Medical and Surgical Treatments
Treatment depends entirely on the cause. For congestion related to infections or mild allergies, the home measures already described are usually sufficient while the underlying problem resolves. Persistent allergic rhinitis in slightly older infants may warrant a trial of specific interventions guided by your pediatrician.
For structural causes, surgery is often the definitive treatment. Bilateral choanal atresia typically requires emergency stabilization in the neonatal intensive care unit followed by surgical correction. The current standard approach is endoscopic surgery through the nose, where the surgeon opens the blocked passage and creates a new airway. Techniques have improved significantly; adequate widening of the new passage and the use of mucosal flaps to cover the raw area have been found to improve outcomes and reduce the chance of the passage narrowing again.4PubMed Central. Practical Tips for Surgical Management of Bilateral Choanal Atresia
Pyriform aperture stenosis is managed differently depending on severity. Mild cases may be watched with supportive care while the baby grows and the nasal passages naturally widen. More severe cases that compromise breathing and feeding require surgical widening of the bony opening.5PubMed Central. Nasal Pyriform Aperture Stenosis in a Newborn: When to Operate
Enlarged adenoids, which are less common in true newborns but become a frequent cause of nasal obstruction in older infants and toddlers, are treated with adenoidectomy when they are large enough to significantly block the airway. This is one of the most commonly performed pediatric surgeries, and the improvement in nasal breathing after removal is usually dramatic.
When “Normal” Newborn Sounds Are Not Mouth Breathing
New parents often mistake normal newborn breathing noises for signs of obstruction. Newborns are naturally noisy breathers. Their airways are small, and turbulent airflow through narrow nasal passages creates snuffling, snorting, and whistling sounds that can sound alarming but are perfectly normal. This is sometimes called “nasal congestion of the newborn” or periodic breathing, where a baby breathes rapidly for a stretch, pauses for a few seconds, then resumes. These pauses are not apnea as long as they last fewer than about 20 seconds and are not accompanied by color changes or a drop in heart rate.
True mouth breathing looks different from noisy nasal breathing. A mouth-breathing baby has the mouth visibly open during rest, and you may notice the chest pulling in more than usual with each breath (retractions), a sign that the baby is working harder to move air. The distinction between “my baby sounds congested” and “my baby cannot breathe through the nose” is the key one. If you can see your baby’s chest and belly rising and falling rhythmically with the mouth closed, that snorting sound is likely just air moving through a small nose. If the mouth is consistently open at rest and during sleep, that is worth bringing up at your next pediatrician visit, or sooner if feeding or breathing seems truly strained.
The Role of the Nose Beyond Simple Airflow
The nasal passages are not just tubes that carry air. The internal structures, including the bony turbinates and curved passages, create turbulence that forces air to contact the moist lining of the nose. This contact warms the air to body temperature and adds moisture, protecting the delicate tissue of the lungs. The coarse hairs inside the nostrils and the sticky mucus lining trap dust, bacteria, and other particles before they can reach the lower airways.13PubMed Central. Know Your Nose: A Narrative Review of the Developmental and Functional Impact and Importance of the Nose, Nasal Breathing and Techniques on Health and Emotional Wellbeing When a baby breathes through the mouth, all of this conditioning is bypassed. Cold, dry, unfiltered air goes straight to the lungs, increasing susceptibility to respiratory irritation and infection.
The nitric oxide produced in the sinuses and carried to the lungs during nasal breathing has effects beyond blood vessel dilation. It also has antimicrobial properties, helping to kill bacteria and viruses in the airways. A baby who is chronically mouth breathing misses out on this built-in defense system at a time when the immune system is still immature and particularly vulnerable. This is one reason that nasal breathing is not just a preference or a developmental curiosity; it is a functional advantage that newborns are anatomically built to rely on, and restoring it when something goes wrong should be treated as a genuine medical priority.