Mouth Breathing: Effects on Health and How to Stop It

Last updated: April 2026 | Written by the DELIM Sleep Team

Most of us breathe through our mouths at some point — when we have a cold, during intense exercise, or simply out of habit. But for millions of people, mouth breathing has become the default, happening not just during the day but throughout the night as well. And while it might seem like a minor quirk, chronic mouth breathing has real, measurable consequences for your health, sleep, and wellbeing.

This guide breaks down exactly what happens when you breathe through your mouth instead of your nose, why nasal breathing is significantly healthier, and practical steps you can take to make the switch — including during sleep.

Nose vs. Mouth: Why It Matters How You Breathe

Your nose is a highly sophisticated breathing apparatus. It's not just a hole in your face — it's a multi-function filter and conditioning system that the mouth simply cannot replicate. When you breathe through your nose:

• Air is filtered: Tiny hairs (cilia) and mucous membranes trap dust, pollen, bacteria, and viral particles before they reach your lungs.
• Air is humidified: Nasal passages add moisture to incoming air, protecting the delicate tissues of your lungs and airways.
• Air is warmed: Nasal passages heat incoming air to body temperature before it reaches your lungs, reducing respiratory stress in cold environments.
• Nitric oxide is produced: The nasal sinuses produce nitric oxide — a molecule that dilates blood vessels, improves oxygen absorption, and has antiviral and antibacterial properties. Mouth breathing bypasses this entirely.
• Breathing rate is regulated: Nasal breathing creates more airway resistance than mouth breathing, which slows and deepens breathing and activates the parasympathetic (rest-and-digest) nervous system.

Breathing through your mouth bypasses all of these benefits. The mouth was designed for eating and speaking — not for sustained breathing. When it becomes your primary breathing route, your body pays a cost.

Physical Health Effects of Chronic Mouth Breathing

Dental and Oral Health Problems

One of the most immediate and well-documented effects of chronic mouth breathing is damage to oral health. When you breathe through your mouth, airflow dries out the saliva that coats your teeth and gums. Saliva is critical — it neutralises acid, washes away bacteria, and remineralises tooth enamel. Without adequate saliva:

• Cavity risk increases significantly
• Gum disease (gingivitis and periodontitis) is more likely
• Chronic bad breath (halitosis) develops as bacteria multiply in a dry oral environment
• Sore throat and dry mouth become regular morning occurrences

Reduced Oxygen Efficiency

Counterintuitively, breathing more air through your mouth doesn't mean you get more oxygen. Nitric oxide produced in the nasal sinuses plays a critical role in oxygen exchange — it causes blood vessels in the lungs to dilate, allowing more oxygen to transfer from the air into your bloodstream. Without this nitric oxide, your oxygen uptake per breath is less efficient even if you're breathing more air volume.

Facial Development Effects in Children

In children, chronic mouth breathing has particularly significant structural consequences. Because the face is still developing, habitual mouth breathing changes the mechanical forces acting on facial bones and tissues, often leading to:

• Narrow, high-arched palate (roof of the mouth)
• Crowded or misaligned teeth (malocclusion)
• Elongated facial structure ("long face syndrome")
• Retracted lower jaw and chin
• Increased risk of sleep-disordered breathing in adulthood

A 2014 review in the journal Dental Press Journal of Orthodontics concluded that mouth breathing in childhood is associated with significant changes in craniofacial structure that have long-term consequences for dental health and airway function. Early intervention — treating the underlying cause of mouth breathing — is essential.

Elevated Blood Pressure and Cardiovascular Risk

Chronic mouth breathing is associated with lower blood nitric oxide levels, which contributes to increased vascular resistance and elevated blood pressure. A 2019 study in the Journal of Human Hypertension found an association between habitual mouth breathing and higher systolic blood pressure in adults. The mechanism is primarily the loss of nitric oxide-mediated vasodilation.

Increased Infection Risk

The nose's filtration system removes a significant proportion of airborne pathogens before they reach the lungs. Mouth breathers receive unfiltered, unhumidified air directly into their airways, increasing exposure to allergens, bacteria, and viruses. People who habitually breathe through their mouths tend to experience more frequent upper respiratory infections and greater severity of symptoms.

How Mouth Breathing Affects Sleep

Nighttime mouth breathing is particularly damaging because it occurs during the 7 to 9 hours when your body is meant to be in its most restorative state — and you're not conscious to notice or correct it.

Snoring

Mouth breathing during sleep is one of the primary mechanical causes of snoring. When you breathe through your mouth while lying down, the jaw drops and the tongue falls backward, partially obstructing the airway. As air moves past these soft tissues at speed, they vibrate — producing the characteristic snoring sound. Nasal breathing keeps the mouth closed and the tongue in a natural resting position against the upper palate, keeping the airway clearer.

Worsened Sleep Apnea

In people with obstructive sleep apnea (OSA), mouth breathing significantly worsens the severity of the condition. A 2014 study published in the Journal of Clinical Sleep Medicine found that mouth breathing during sleep was associated with significantly worse apnea-hypopnea index (AHI) scores — a direct measure of sleep apnea severity. Encouraging nasal breathing is an important component of sleep apnea management.

Fragmented Sleep and Daytime Fatigue

Even without formal sleep apnea, mouth breathing disrupts sleep quality. Dry mouth, throat irritation, and subtle drops in blood oxygen from less efficient gas exchange all contribute to micro-arousals — brief moments of wakefulness that fragment sleep architecture without you fully waking up. The cumulative effect is reduced time in slow-wave and REM sleep, leaving you feeling unrested despite adequate time in bed.

Dry Mouth and Morning Symptoms

Waking up with a dry, sticky mouth, sore throat, or bad breath are hallmark signs of nighttime mouth breathing. Over time, the chronic dryness accelerates dental decay and can contribute to oral infections.

Mental and Cognitive Effects of Mouth Breathing

The effects of mouth breathing aren't purely physical — they extend to mood, cognition, and stress.

Because mouth breathing activates a faster, more shallow breathing pattern, it tends to keep the sympathetic ("fight or flight") nervous system slightly elevated. Chronically elevated sympathetic tone means higher baseline cortisol and adrenaline levels, which contribute to anxiety, irritability, and difficulty relaxing. Nasal breathing, by contrast, naturally activates the parasympathetic nervous system, promoting calm and reducing physiological stress.

In children, the cognitive effects of poor sleep caused by nighttime mouth breathing are particularly pronounced. Research has linked sleep-disordered breathing in children to attention difficulties, hyperactivity, and academic underperformance — in some cases mimicking or exacerbating ADHD symptoms. Treating the underlying breathing issue often produces significant improvements in behaviour and academic performance.

How to Stop Mouth Breathing: Practical Strategies

1. Identify and Address the Root Cause

The most important step is understanding why you're mouth breathing. Common causes include:

• Chronic nasal congestion from allergies, sinusitis, or a deviated septum — see a GP or ENT for assessment and treatment
• Nasal polyps — small, benign growths in the nasal passages that block airflow and require medical treatment
• Enlarged adenoids or tonsils — particularly common in children; may require surgical removal
• Habit — some people mouth breathe even when their nasal passages are clear, simply because the habit has become established

2. Nasal Hygiene and Allergy Management

Keeping your nasal passages clear significantly reduces the need or tendency to mouth breathe. Practical measures include:

• Daily saline nasal rinse (neti pot or squeeze bottle) to flush allergens and mucus
• Nasal corticosteroid sprays (e.g. Flonase / fluticasone) for allergy-related congestion — available over the counter in the UK
• Antihistamines for seasonal allergies
• Keeping the bedroom free of dust, pet dander, and other allergens — an air purifier with a HEPA filter helps
• Using a humidifier in winter when indoor air becomes very dry and can irritate nasal passages

3. Breathing Retraining Exercises

Breathing exercises can help retrain the habit of nasal breathing over time. The Buteyko breathing method, developed in the 1950s by Ukrainian physician Konstantin Buteyko, focuses specifically on reducing breathing volume and restoring nasal breathing patterns. Multiple studies have found Buteyko technique to be effective in reducing asthma symptoms and improving nasal breathing habits. A certified practitioner can guide you through the technique, or introductory resources are available online.

Simpler practices include: consciously keeping your lips together and breathing through your nose during low-intensity activities; practising slow, deep nasal breaths during moments of rest; and incorporating yoga or meditation, both of which emphasise nasal breathing.

4. Mouth Taping for Nighttime Nasal Breathing

For people who breathe through their mouths at night — even when they can breathe comfortably through their nose during the day — mouth taping is one of the most practical and evidence-supported interventions available.

Mouth taping involves applying a gentle, skin-safe adhesive strip over the lips before sleep to keep the mouth closed and encourage nasal breathing. A 2022 study published in the journal Healthcare found that porous mouth tape used during sleep significantly reduced snoring frequency and the apnea-hypopnea index in patients with mild sleep apnea, while also improving sleep quality scores.

DELIM Mouth Tape is designed specifically for this purpose — it uses a gentle, hypoallergenic adhesive that's comfortable on the skin, breathable, and easy to remove in the morning. Unlike improvised alternatives, it's made from a porous material that allows airflow if needed, making it safe for nighttime use in people who can breathe comfortably through their nose.

Important: Mouth taping is suitable for healthy adults who can breathe comfortably through both nostrils. If you have untreated moderate or severe sleep apnea, significant nasal obstruction, or any respiratory condition, consult your GP or a sleep specialist before trying mouth taping.

Read our full guide: Mouth Taping for Beginners: What to Know Before Trying

5. Sleep Position

Sleeping on your back tends to promote mouth breathing and worsen snoring, because gravity pulls the jaw open and the tongue back into the airway. Side sleeping naturally helps keep the airway more open and makes it easier to maintain nasal breathing. If you consistently wake with dry mouth or snore when on your back, try sleeping on your side — a body pillow placed along your front can help you maintain the position through the night.

When to See a Doctor

While lifestyle changes and tools like mouth taping can meaningfully improve mouth breathing habits, some underlying causes require medical assessment. You should see a GP, ENT, or sleep specialist if:

• Your nasal passages feel chronically blocked even when you don't have a cold
• You or your partner notices frequent pauses in breathing during sleep (a possible sign of sleep apnea)
• You snore loudly or feel unrefreshed despite adequate sleep duration
• Your child breathes through their mouth most of the time, snores, or shows behaviour changes consistent with poor sleep
• You have recurrent sinus infections, nosebleeds, or significant facial pressure

Frequently Asked Questions

Is mouth breathing bad for you?

Yes — chronic mouth breathing has documented negative effects on oral health (tooth decay, gum disease, bad breath), sleep quality (snoring, sleep apnea, fragmented sleep), respiratory health (reduced oxygen efficiency, increased infection risk), and in children, facial development. Occasional mouth breathing, such as during intense exercise or when congested, is normal and not a concern.

Can mouth breathing change your face shape?

In children whose facial bones are still developing, yes — chronic mouth breathing can alter craniofacial development, contributing to a narrow palate, misaligned teeth, and an elongated facial structure. In adults, the bones are fully formed and structural change from mouth breathing alone is unlikely, though soft tissue changes and dental effects still occur.

How do I know if I'm mouth breathing at night?

Common signs of nighttime mouth breathing include waking with a dry or sticky mouth, sore throat in the morning, frequent bad breath, snoring (confirmed by a partner or a sleep tracking app), and waking up feeling unrested despite a full night of sleep. You can also apply a small piece of mouth tape before sleep — if you consistently pull it off during the night, that suggests you're trying to open your mouth.

Does mouth tape actually work for mouth breathing?

For people who breathe comfortably through their nose during the day, mouth tape is an effective tool for maintaining nasal breathing during sleep. A 2022 study in Healthcare found that porous mouth tape reduced snoring and improved breathing metrics in mild sleep apnea patients. Many users also report reduced dry mouth, better sleep quality, and quieter nights. It is not a treatment for sleep apnea or structural nasal obstruction.

What causes mouth breathing?

The most common causes are chronic nasal congestion from allergies or sinusitis, anatomical factors such as a deviated septum or nasal polyps, enlarged adenoids or tonsils (particularly in children), and established breathing habits. In some people, mouth breathing persists as a habit even after the original cause is resolved.

How long does it take to switch to nasal breathing?

For habit-based mouth breathing, consistently practising nasal breathing during the day and using tools like mouth tape at night, most people notice meaningful improvement within 2 to 4 weeks. For mouth breathing caused by structural or allergic issues, treating the underlying cause first is essential — improvement often follows quickly once the nasal obstruction is resolved.

Sources

• Jefferson, Y. (2010). Mouth breathing: adverse effects on facial growth, health, academics, and behaviour. General Dentistry. pubmed.ncbi.nlm.nih.gov
• Hsu, Y.B. et al. (2014). Mouth breathing, another risk factor for obstructive sleep apnea: The Taipei Bus Driver Survey. Journal of Clinical Sleep Medicine. pubmed.ncbi.nlm.nih.gov
• Lee, S.H. et al. (2022). Efficacy of Mouth Taping on Snoring. Healthcare. pubmed.ncbi.nlm.nih.gov
• Fitzpatrick, M.F. et al. (2003). Effect of nasal or oral breathing route on upper airway resistance during sleep. European Respiratory Journal. pubmed.ncbi.nlm.nih.gov
• Lundberg, J.O. (2008). Nitric oxide and the paranasal sinuses. The Anatomical Record. pubmed.ncbi.nlm.nih.gov
• Sleep Foundation. Mouth Breathing During Sleep. sleepfoundation.org
• Cleveland Clinic. Mouth Breathing: Symptoms, Causes and Treatments. health.clevelandclinic.org