Does mouth breathing cause bad breath?

Your nose is built for breathing; it warms, moistens and filters air. When you breathe through your mouth instead, a steady stream of air evaporates saliva. Saliva is what normally keeps the tongue and teeth rinsed, so a dry mouth gives bacteria on the back of the tongue an easier time producing sulfur gases.

It is worst at night. Saliva flow already drops during sleep, and sleeping with your mouth open dries it further, which is why mouth breathers often wake with a parched mouth and strong morning breath. Cleveland Clinic notes mouth breathing in adults can cause persistent morning breath.

Cleveland Clinic lists these symptoms in adults and children:

• Bad breath
• Dry mouth, especially on waking
• Drooling on your pillow
• Snoring
• Hoarseness
• Feeling tired during the day

In children, watch for an open mouth during the day, snoring and restless sleep. Cleveland Clinic notes long-term mouth breathing in children can affect how the face and teeth develop.

Most studies have been in children. A study of 10- to 15-year-olds found mouth breathers were about three times as likely to have bad breath as nasal breathers, even though their rates of tooth decay and gum inflammation were similar. A Brazilian study of children also found a significant link between mouth breathing and bad breath. Together they suggest the dryness itself, not just poor hygiene, drives the smell.

See allergies and bad breath and sinus infection bad breath for more on those causes.

• Clear your nose before bed with saline rinses, and treat allergies if you have them.
• Use a humidifier at night, which Cleveland Clinic suggests if you breathe through your mouth while sleeping.
• Keep water by the bed and sip if you wake with a dry mouth.
• Clean your tongue every morning. Overnight dryness leaves a thicker coating, and removing it takes away much of the smell.
• Brush and clean between your teeth before bed, so bacteria have less to feed on overnight.
• Avoid alcohol before bed, which the NHS links with snoring.
• Be cautious with mouth taping. It is popular online but not well studied, and it is not safe if your nose is blocked or you may have sleep apnea. Ask a doctor first.

Cleveland Clinic advises seeing a healthcare provider if you notice dry mouth, bad breath or pillow drool, or if your child often breathes through their mouth. The NHS advises seeing a GP if your breathing stops and starts during sleep, you make gasping or choking noises, or you always feel very tired during the day, since these can be signs of sleep apnea.