A 2026 crossover study in Vascular Health and Risk Management put 45 healthy young men through matched sessions of nasal and mouth breathing and measured their blood vessels afterward.
When the men breathed through the nose, the researchers found a 6.35 percent increase in pulse propagation time and a 4.46 percent widening of the brachial artery, both signs of improved vascular function.
Mouth breathing produced neither change.
The brain reacts to the switch too. A study published April 3, 2026 in Scientific Reports used functional brain imaging to compare nasal and mouth breathing, and found that nasal airflow stabilized an integrated brain state involving the default mode, frontoparietal, salience and limbic networks.
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Mouth breathing pushed the same networks toward fragmentation, a pattern the authors say aligns with earlier evidence that chronic mouth breathing is linked to impaired attention.
Jaw and posture
The musculoskeletal picture is now clearer as well.
A systematic review in adults, published in The Laryngoscope in 2026, concluded that mouth breathers had a higher prevalence of temporomandibular joint dysfunction, meaning pain or clicking in the joint that connects the jaw to the skull.
They also carried the head further forward on the neck, showed greater curvature in the lower back, and chewed less efficiently, with weaker activity in the main chewing muscles and more strain in the muscles under the jaw.
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None of the included studies looked directly at pain, so the review cannot say mouth breathing causes it.
But the postural and muscular pattern the researchers describe is the same one physical therapists see in patients with chronic neck and jaw complaints.
The problem in your mouth
Saliva is the mouth's first defense against decay.
It rinses food particles off the teeth and buffers the acids that dissolve enamel.
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When you breathe through the mouth for hours at a time, especially during sleep, saliva evaporates and that defense weakens.
The result over time is more plaque, more cavities and a higher risk of gum disease.
Why people breathe through the mouth
Most of the time the nose is blocked.
Common culprits, the Cleveland Clinic notes, include a deviated septum, meaning the cartilage and bone dividing the two nasal passages leans to one side and narrows the airway.
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Chronic congestion from allergies, colds or sinusitis is another.
So are swollen turbinates, the ridges inside the nose that regulate airflow, and enlarged adenoids or tonsils, which are more common in children.
Habit can also keep the pattern going in people who once had a blocked nose and never returned to breathing through it.
Treatment usually starts with what is causing the blockage.
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Options range from antihistamines and steroid nasal sprays to septoplasty, a surgery that straightens the septum, or turbinate reduction.
Myofunctional therapy, a form of exercise for the tongue and facial muscles, is often added to retrain the closed-lip resting posture.
A note on mouth taping
The sleep-hack version, taping the lips shut at night, has drawn wide social-media attention.
A 2025 systematic review in PLOS One covering 10 studies and 213 patients found only modest evidence of benefit, mostly in mild sleep apnea, and flagged a serious risk of asphyxiation in anyone with a blocked nose or a tendency to reflux.
The authors concluded that current data do not support mouth taping as a sound clinical intervention for the general population.
Anyone considering it should first ask a doctor to check whether the nose is actually open.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.