What does this mean?
Your nose warms, moistens and filters the air you take in. When that route is blocked, the body switches to breathing through the mouth. Air passing through the mouth is dry and unfiltered; it constantly dries the thin film of saliva on the surface of the front teeth and the gums. Bacterial plaque takes hold more easily where the surface dries out, and redness, swelling and bleeding of the gums become obvious, particularly on the upper front teeth.
What separates this symptom from the ones that belong to the night alone is that it carries on during the day as well. In someone whose mouth only falls open in sleep, the problem is usually a narrowing of the airway during sleep. If the lips do not come together during the day either, and the mouth stays open while you are resting or reading, a lasting obstruction in the nasal passage or a settled habit is considered. Watching in the mirror for a few minutes to see whether your lips rest closed on their own is usually enough to draw this distinction.
In children who are still growing, mouth breathing does not only affect the inside of the mouth. Because the tongue rests low all the time, it does not support the upper jaw from within; the palate can become narrow, the upper front teeth can tip forwards and the lower part of the face can grow longer. Because these changes are harder to correct once they have settled, looking into the cause early is advised in children.
Mouth breathing is most often the result of a blocked nose, but it can carry on as a habit even after the blockage has cleared. The headings below bring together the causes seen most often.
Likely causes
What helps at home?
- Check now and then during the day whether your lips are closed; keeping your mouth shut while your nose is clear stops the habit from settling in.
- Keep up your water intake and avoid sipping sugary drinks through the day; the risk of decay climbs faster in a dry mouth.
- Do not keep using decongestant nasal sprays and drops for days on end without a doctor's advice; some can make the blockage worse with long use.
- Do not turn to practices that circulate online, such as taping the mouth shut; if the nasal passage really is blocked, this makes breathing harder.
- If your child snores in their sleep, stops breathing, or has a restless night.
- If the blockage is on one side of the nose only and comes with a smelly or bloody discharge.
- If you often have to sit up at night in order to breathe.
- If your gums have started to bleed and the redness does not settle despite regular brushing.
- If not being able to close the mouth is making speaking, swallowing or eating difficult.
Frequently asked questions
- Does mouth breathing really harm the teeth?
- What does the harm is not the air itself, but the drying of the saliva. Saliva buffers the acid in the mouth and helps repair the surface of the enamel; that protection falls away in an area that stays dry. This is why inflammation at the gum margin of the upper front teeth, and decay, are seen more often in people who breathe through the mouth.
- My child sleeps with their mouth open. Will it sort itself out as they grow?
- It cannot always be expected to settle on its own. If the cause is an obstruction such as enlarged adenoids or tonsils, the habit continues until that obstruction is dealt with. The period in which the jaws grow fastest is also limited, so looking into the cause is advised rather than waiting.
- Which clinician should I see first?
- If a blocked nose is the main issue, an ear, nose and throat assessment is the first step. A dentist assesses the consequences inside the mouth, the width of the palate and the bite; in children, whether orthodontic monitoring is needed is decided at that assessment. The two departments often work together.
This content is for general information and does not replace an in-person examination. Symptoms overlap between conditions, and a diagnosis can only be made clinically.