Mouth-breathing: Why it’s bad for you and how to stop

Breathing through your nose has long been considered superior to breathing through your mouth. ‘Mouth-breather’ has been used as an insult for a stupid person since at least 1915, and people who do it are sometimes said to be unattractive. But while training yourself to breathe through the nose might not make you beautiful and smart, it could have very real impacts on your health, from your teeth to your fitness.

We spoke to science journalist James Nestor on the Instant Genius podcast. He’s the author of Breath: The New Science of a Lost Art, which was shortlisted for the Royal Society Science Book Prize 2021. He explained why we’re the “worst breathers in the animal kingdom”, what mouth-breathing does to your health, and how you can train yourself to breathe through your nose.

Why does it matter how we breathe?

Our body takes care of our breathing automatically, so you’d think we’d default to breathing in the way that’s best for us. Unfortunately, that’s not necessarily the case. “Every time we need to breathe, we do it unconsciously. But the problem is, we could be doing it improperly or inefficiently, and that could be our habit,” says Nestor. “And then we carry this habit around with us our whole lives, and we can suffer from some very serious health consequences if we aren't breathing correctly.”

Even worse, this seems to be a uniquely human problem. “We are the worst breathers in the animal kingdom,” says Nestor. “That's quite a claim. But if you don't believe me, go into the wild and look at how animals are breathing.

“If you look at primates, they breathe into their stomachs. They breathe very fluidly, very calmly. If you look at a cheetah running at 100 kilometres an hour, it is breathing through its nose very calmly.”

Even our ancestors breathed differently to us. We can look at the skulls of ancient people and compare their facial structures to ours, with surprising results.

“I was invited to go to the University of Pennsylvania to the Morton Collection, which is the largest collection of pre-industrial skulls in the world. Thousands and thousands of these things; skulls from Africa, from Asia, from South America, from Polynesia, all over the place,” said Nestor.

“And every single one of them had perfectly straight teeth. So, crooked teeth is a modern problem. And the first thing you ask is, well, why do we have crooked teeth? We have crooked teeth because our mouths have grown so small. And when our mouths have grown so small, teeth have nowhere to grow in straight, so they grow in crooked. With that small mouth, you also have a smaller airway and the breathing and respiratory problems that come with that.”

Read more about animals' breathing:

• How do ants breathe?
• How do baby birds breathe inside their eggs?
• ‘Scuba-diving’ lizards breathe underwater by attaching air bubbles to their snouts

Why is it better to breathe through the nose?

You might think that air is air, and as long as we’re getting enough of it into our bodies, it doesn’t make a difference how we breathe it. But that’s not entirely true – the mechanics of breathing mean that air that came in through the nose is different from air from the mouth.

“The reason why this is so important is because when you breathe through the nose, you are forcing air through all of these very intricate structures. And as that air is forced through these structures, it's heated up, it’s humidified, it's pressurised, and it's filtered,” Nestor says. “So, that air, when it gets to your lungs, can be so much more easily uploaded into your bloodstream.

“We can extract about 20 per cent more oxygen breathing through our noses than we can equivalent breaths through our mouths.” That’s no small difference, especially when you’re exercising. A 1996 study showed that breathing exclusively through the nose during exercise not only lowers your breathing, but also significantly increases your endurance. And on top of that, you might even feel more comfortable doing it: participants felt like they were exerting themselves less.

The nose’s filtration system also plays an important role in your immune system. First, air passes the nasal hairs in your nostrils, which capture pollen and other allergens. A study published in 2011 showed that hay fever sufferers with a greater density of nasal hairs were less likely to develop asthma.

The air then passes into the nasal cavity, which is lined with mucus and hair-like filters called cilia. These collect dust, soot, debris and even bacteria. “The nose is our first line of defence, including against viruses and bacteria,” Nestor says.

Can you train yourself to breathe through the nose?

Some people who breathe through the mouth do so because of severe damage to the nose, such as a deviated septum or nasal polyps. If that’s the case, talk to your doctor. They may be able to recommend treatments such as surgery or steroids, depending on the cause.

“But for the vast majority of us, it comes down to a habit,” says Nestor. “Our nose will respond to what is given to it. So, our noses are covered with erectile tissue, so this tissue will flex, it will flex open, and it will flex closed. The more you breathe through the mouth, the more this tissue is going to stay closed. The more you start breathing through the nose, the more this tissue opens.

“It's really a ‘use it or lose it’ organ.”

If you’re already losing it, you can get it back, using it won’t be easy at first. “It's miserable usually for four weeks or even months. But once you make it over that hump, as we've seen time and time again, performance often increases, recovery decreases, and you're able to function so much more efficiently.”

During the day, training your breathing is easy enough: when you notice yourself breathing through the mouth, make a conscious effort to close your mouth and breathe through the nose instead. Nose-breathing while you sleep, however, is a different matter.

One thing you can try is to place a small piece of surgical tape over your lips when you go to bed. “I was told by a Stanford researcher that she prescribes this to all of her patients,” says Nestor. “The technology is pretty simple, but it is absolutely transformative to my sleep. And this is the one thing that I've heard from literally thousands of people that this is the biggest hack that they've had for their health.”

If you’re not sure whether you’re a mouth-breather at night, pay attention to whether you wake up with a dry mouth. If you need to drink a lot of water, or you have bad breath in the morning, it might be because you’re breathing through your mouth. Snoring can also be an effect of mouth-breathing, so ask a partner if they’ve heard you.

The biggest effect of mouth-breathing at night is the impact it can have on the quality of your sleep. You could consider using a tracker to measure your sleep quality to make sure you’re not missing out on vital rest.