Mouth taping has again become a popular bedtime trend on social media — just as it trended a few years ago.

The idea is to tape the mouth shut at night to promote nasal breathing, which some experts claim can have health benefits.

Others, however, warn of potential risks and questionable results.

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The Sleep Foundation, based in Seattle, Washington, says the benefits of mouth taping are "mostly anecdotal," with few studies backing up the benefits.

Potential benefits

"The main proposed benefit of mouth taping is promoting nasal breathing, which helps filter and humidify air and may reduce snoring or dry mouth for some individuals," sleep expert Wendy Troxel, Ph.D. — a RAND Corporation senior behavioral specialist and licensed clinical psychologist in Utah — told Fox News Digital.

Breathing through the nose helps people absorb more oxygen, according to Todd Anderson, sleep and wellness expert and founder of Dream Performance & Recovery in Nashville.

When you breathe out through your mouth all night, you're expelling most of the carbon dioxide in your body, Anderson said — but it can be beneficial to have some CO2 in the system.

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"When you start exercising, you're under stress and your CO2 starts to rise," he told Fox News Digital. 

"So the more comfortable you are with carbon dioxide in your system, the more adaptable to stress your body is."

Breath is like the "steering wheel" of the nervous system.

Anderson said breath is like the "steering wheel" of the nervous system, as breathing through the nose promotes longer exhalations and relaxes the body.

"Your nose [also] produces nitric oxide, which you breathe down into your lungs. That expands your blood vessels and relaxes your cardiovascular system," he said. "Top to bottom, it calms your body down. That's why it impacts sleep in such a positive way."

Some claim that using the tape could also help achieve a more defined jaw structure and could protect dental health, Anderson noted, as mouth breathing leads to dryness and more acidity, which can break down tooth enamel.

‘Considerable caution’

Sleep expert Troxel said she approaches mouth taping with "considerable caution" — as scientific evidence shows that its effectiveness is "limited."

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"While some people report less snoring or better sleep, most of these claims are anecdotal and not well-supported by rigorous research with large and diverse samples," she told Fox News Digital.

While there is some "preliminary evidence" that mouth taping can reduce snoring for some sleep apnea patients, Troxel noted that the overall effect is "modest."

She added there is "no strong evidence" that mouth taping changes jaw shape.

For those who have nasal congestion, blockages or allergies, Troxel and Anderson agreed that mouth taping is not recommended, as it can make it harder to breathe at night.

"This can lead to feelings of anxiety and disrupted sleep — and in some cases, it may lower oxygen levels while sleeping," Troxel warned. 

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One big concern is that using mouth tape may delay or prevent people from getting proper treatment for sleep apnea, she added, which could pose serious health risks.

Anderson also recommended against mouth taping for people who are overweight, those who drink alcohol or other substances, and those who are feeling sick.

Troxel encouraged those who experience mouth breathing or snoring to consult with a healthcare provider to address any underlying issues.

"Treating the root cause is safer and more effective than taping the mouth shut," she said.

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"For otherwise healthy, low-risk individuals who do not have sleep apnea and want to experiment with mouth taping, I suggest approaching it scientifically and with caution."

"Treating the root cause is safer and more effective than taping the mouth shut."

For those who do decide to try it, Troxel suggested testing the tape on the skin first to check for irritation, using medical-grade tape, or considering a tape with a slit so that the mouth is not fully covered.

Anderson added that consumers should consider where the mouth tape is made and what adhesive is used, to prevent skin irritation and allergic reactions. 

The Sleep Foundation cautions on its website that some side effects of mouth taping include difficulty breathing, skin irritation and anxiety.

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Using a sleep tracker before and during the use of mouth tape for a few weeks could help gauge how it’s working, Troxel advised.

"If you do not see improvements, that’s your answer — it may not be effective for you," she said. "Always stop immediately if you experience discomfort or difficulty breathing."

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There are other ways to promote nasal breathing, according to Troxel — including targeted exercises.

"Alternating nostril breathing or belly breathing during the day can help train your body to breathe through your nose more naturally at night," she said. 

"It's also a great strategy to manage stress and promote relaxation."