Under 'normal' circumstances breathing through the mouth only becomes necessary when you have nasal congestion due to allergies or a cold. Also, when you are exercising strenuously, mouth breathing can help get oxygen to your muscles faster.

Even so, breathing through the mouth all the time, including when you’re sleeping, can lead to problems.

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In children, mouth breathing can cause crooked teeth, facial deformities, or poor growth. In adults, chronic mouth breathing can cause bad breath and gum disease. It can also worsen symptoms of other illnesses.

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How do I know if I am breathing through my mouth?

You may not realize that you’re breathing through your mouth instead of your nose, especially while you sleep. People who breathe through their mouth at night may have the following symptoms:

• snoring

• dry mouth

• bad breath (halitosis)

• hoarseness

• waking up tired and irritable

• chronic fatigue

• brain fog

• dark circles under the eyes
   

Symptoms in children

For parents, it’s important to look for signs of mouth breathing in their children.

A child may not be able to communicate their symptoms. Like adults, children who are mouth breathers will breathe with their mouth open and will snore at night. Children who breathe through their mouths for most of the day may also have the following symptoms:

• slower than normal growth rate

• irritability

• increased crying episodes at night

• large tonsils

• dry, cracked lips

• problems concentrating at school

• daytime sleepiness
   

Children who exhibit problems concentrating at school are often misdiagnosed with attention deficit disorder (ADD) or hyperactivity.

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What causes mouth breathing?

The underlying cause of most cases of mouth breathing is an obstructed (completely blocked or partially blocked) nasal airway.

In other words, there’s something preventing the smooth passage of air into the nose. If your nose is blocked, the body automatically resorts to the only other source that can provide oxygen — your mouth.

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There are many causes of a blocked nose. These include:

• nasal congestion caused by allergies, a cold, or a sinus infection

• enlarged adenoids and tonsils

• deviated septum

• nasal polyps, or benign growths of tissue in the lining of your nose

• enlarged turbinates

• the shape of the nose

• the shape and size of the jaw

• tumors (rare)
   

Some people develop a habit of breathing through their mouth instead of their nose even after the nasal obstruction clears. For some people with sleep apnea, it may become a habit to sleep with their mouth open to accommodate their need for oxygen.

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Stress and anxiety can also cause a person to breathe through their mouth instead of their nose. Stress activates the sympathetic nervous system leading to shallow, rapid, and abnormal breathing.

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How is mouth breathing diagnosed?

There’s no single test for mouth breathing. A doctor might diagnose mouth breathing during a physical examination when looking at the nostrils or during a visit to find out what’s causing persistent nasal congestion. They may ask questions about sleep, snoring, sinus problems, and difficulty breathing.

A dentist may diagnose mouth breathing during a routine dental examination if you have bad breath, frequent cavities, or gum disease.

If a dentist or doctor notices swollen tonsils, nasal polyps, and other conditions, they may refer you to a specialist, like an ear, nose, and throat (ENT) doctor for further evaluation.

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Can mouth breathing lead to health problems?

Mouth breathing is very drying. A dry mouth means that saliva cannot wash bacteria from the mouth. This can lead to:

• bad breath (halitosis)

• periodontal disease, such as gingivitis and tooth cavities

• throat and ear infections
   

Mouth breathing may result in low oxygen concentration in the blood. This is associated with high blood pressure and heart failure. Studies show mouth breathing may also decrease lung function and worsen symptoms and exacerbations in people with asthma.

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In children, mouth breathing can lead to physical abnormalities and cognitive challenges. Children who aren’t treated for mouth breathing can develop:

• long, narrow faces

• narrow mouths

• gummy smiles

• dental malocclusion, including a large overbite and crowded teeth

• poor posture
   

Additionally, children who breathe through their mouths often don’t sleep well at night. Poor sleep can lead to:

• poor growth

• poor academic performance

• inability to concentrate

• sleep disorders