Published in Healthcare in 2022, researchers at Chang Gung Memorial Hospital in Taiwan tested the effect of mouth taping on 20 confirmed mouth-breathers diagnosed with mild obstructive sleep apnea (OSA), meaning they had between 5 and 15 breathing interruptions per hour of sleep.

Participants slept with 3M silicone tape sealing their lips during overnight polysomnography (a comprehensive sleep study that records brain waves, blood oxygen, heart rate, and breathing). Their median apnea-hypopnea index (AHI) - the number of times breathing stops or slows per hour - dropped from 8.3 to 4.7 events per hour. The snoring index and oxygen desaturation index also improved significantly.

Patients with worse baseline scores showed the greatest improvement. The researchers noted that mouth taping forced nasal breathing, which kept the upper airway more stable during sleep. The authors labeled this a preliminary study given the small sample size.

Published in the Annals of the American Thoracic Society in 2022, this prospective crossover pilot study enrolled 21 adults with moderate-to-severe obstructive sleep apnea (AHI between 10 and 50 events per hour). Each participant used a mandibular advancement device (MAD) - a dental appliance that holds the lower jaw forward - both with and without mouth tape.

When mouth tape was added to the MAD, the median AHI dropped to 5.6 events per hour compared to 10.5 with the MAD alone. The difference was statistically significant (p = 0.02). The proportion of patients achieving a treatment target of fewer than 10 events per hour rose from 43% with MAD alone to 76% with MAD plus tape (p < 0.01).

The researchers concluded that mouth leak is a significant factor undermining the effectiveness of oral appliance therapy, and that simple lip taping can substantially improve treatment outcomes by keeping the mouth closed and maintaining nasal breathing.

Published in the Journal of Clinical Sleep Medicine in 2025, this randomized crossover trial enrolled 62 patients with obstructive sleep apnea who used CPAP machines but also breathed through their mouths during sleep. Each participant used CPAP with and without mouth tape for 30 days each, separated by a 1-week washout period.

Adding mouth tape increased average nightly CPAP use by 51.8 minutes per day and increased the frequency of CPAP use by 14.2%. The number of nights with 4 or more hours of use - the clinical definition of adequate CPAP adherence - rose by 17.6%. Participants who used mouth tape were 4.5 times more likely to meet the standard definition of "good CPAP adherence."

Participants also reported significantly less mouth and throat dryness, fewer nighttime awakenings, less snoring, and improved daytime sleepiness scores on the Epworth Sleepiness Scale. The researchers concluded that mouth taping is a simple and effective add-on to improve CPAP therapy compliance.

Published in the European Respiratory Journal in 2003, researchers at Queen''s University in Canada conducted a randomized single-blind crossover study on 12 healthy adults with no history of sleep-disordered breathing. Participants slept on separate nights while breathing exclusively through the nose or mouth, controlled by nasal or oral masks.

Upper airway resistance during sleep was 2.5 times higher with oral breathing (median 12.4 cmH2O/L/s) compared to nasal breathing (5.2 cmH2O/L/s). The obstructive apnea-hypopnea index - measuring how often breathing stopped or slowed per hour - was 43 events per hour during oral breathing versus just 1.5 during nasal breathing.

This nearly 30-fold increase in breathing disruptions occurred in completely healthy people with no sleep disorders. The researchers concluded that the oral breathing route itself destabilizes the upper airway during sleep, providing a physiological basis for interventions like mouth taping that promote nasal breathing.

Published in Nature Medicine in 1995, researchers at the Karolinska Institute in Sweden discovered that the human paranasal sinuses produce nitric oxide (NO) at very high concentrations through an enzyme called inducible nitric oxide synthase located in the sinus lining.

During nasal breathing, this nitric oxide is carried into the lungs with each breath. In the lungs, NO acts as a vasodilator - it widens blood vessels - which increases blood flow to well-ventilated areas and improves the efficiency of oxygen transfer from air into the bloodstream. The researchers called this an "aerocrine" function of the sinuses.

When a person breathes through the mouth, air bypasses the sinuses entirely, and none of this nitric oxide reaches the lungs. This provides a physiological mechanism explaining why nasal breathing (which mouth taping promotes) may improve blood oxygen levels during sleep compared to mouth breathing.

Published in the Journal of Oral Rehabilitation in 2016, researchers at the University of Otago in New Zealand measured the pH and temperature inside the mouths of 10 healthy volunteers as they slept, comparing nights of normal nasal breathing to nights of forced mouth breathing (using a nose clip).

During mouth breathing, the intraoral pH dropped to an average of 3.6 - significantly below the critical threshold of pH 5.5 at which tooth enamel begins to dissolve. During nasal breathing, the pH remained above this danger zone. All 10 participants showed greater pH drops during mouth breathing compared to nasal breathing nights.

The drying effect of air flowing over the teeth and gums during mouth breathing reduces saliva''s protective buffering capacity. Saliva normally neutralizes acids and remineralizes tooth surfaces, but when the mouth dries out, this protection disappears. The researchers concluded that habitual mouth breathing during sleep is a direct cause of dental erosion and cavities, supporting the oral health argument for keeping the mouth closed during sleep.

Published in PLOS ONE in May 2025, researchers at Western University in Canada conducted a systematic review following PRISMA guidelines, searching MEDLINE, Embase, and Google Scholar for studies on mouth taping published between February 1999 and February 2024.

They identified 10 studies covering a total of 213 patients. Across the studies, mouth taping consistently and significantly reduced mouth leak - the amount of air escaping through the mouth during sleep. Two of the ten studies showed statistically significant improvements in the apnea-hypopnea index (AHI) or oxygen desaturation metrics after mouth taping.

The review confirmed that mouth taping is a plausible intervention for people who breathe through their mouths during sleep, particularly as an add-on to existing therapies like CPAP or mandibular advancement devices. However, the authors noted the overall evidence base remains small and heterogeneous, with all studies rated as low quality on the Newcastle-Ottawa assessment scale.

Published in the Archives of Otolaryngology - Head and Neck Surgery in 1996, Swedish researchers studied 42 men who were heavy snorers. Participants used nasal dilators to improve nasal airflow during sleep, and outcomes were measured over 6 months using both self-reports and independent assessments from their female sleeping partners.

The men showed significantly reduced snoring intensity, significantly less daytime tiredness, and improved overall quality of life scores. Crucially, the sleeping partners independently confirmed the improvements, reporting better sleep quality for themselves and noting their partners snored less and seemed more rested in the morning.

A follow-up investigation by the same research group also found that improved nasal breathing in snorers increased nighttime growth hormone secretion and serum IGF-1 (insulin-like growth factor 1) concentrations. This supports the broader principle behind mouth taping: promoting nasal breathing during sleep leads to measurable improvements in sleep quality and daytime functioning.

Published in the American Journal of Respiratory and Critical Care Medicine in 2002, researchers at the Karolinska Institute measured nitric oxide (NO) output from the nasal airways of 10 healthy subjects under different breathing conditions.

During humming - which creates oscillating airflow through the sinuses - nasal NO levels increased up to 15-fold compared to quiet exhalation. Even during normal quiet nasal breathing, significant amounts of NO from the paranasal sinuses are carried into the lower airways with each breath. NO acts as a local vasodilator in the lungs, widening blood vessels to improve the match between airflow and blood flow, which enhances oxygen absorption.

When breathing through the mouth, air bypasses the nasal passages and sinuses entirely, so none of this NO reaches the lungs. The study provides a clear physiological mechanism for why nasal breathing - which mouth taping ensures during sleep - may improve blood oxygenation compared to mouth breathing.