Why does dry mouth cause bad breath?

Dry mouth, or xerostomia, is the feeling that your mouth does not have enough saliva. Cleveland Clinic estimates it affects about 1 in 5 people and becomes more common with age. NIDCR stresses that it is not a normal part of aging, so it is worth finding out why it is happening.

Symptoms include a sticky or dry feeling, thick or stringy saliva, a dry rough tongue, trouble chewing, swallowing or talking, a sore throat, cracked lips and bad breath. Both NIDCR and Cleveland Clinic list bad breath as a symptom.

Saliva does several jobs that keep breath fresh. It physically rinses food particles off the teeth and tongue, dilutes and clears odor gases, and contains substances that help control bacteria. NIDCR notes that dry mouth raises the risk of tooth decay and fungal infections for that reason.

When saliva falls, the coating on the back of the tongue builds up faster and odor-producing bacteria thrive. This is the same reason everyone's breath is worse on waking, since saliva flow drops during sleep. People with chronic dry mouth live with a version of morning breath much of the day.

See our pages on medications and bad breath, mouth breathing and dehydration for more on each.

NIDCR and Cleveland Clinic suggest these self-care steps:

• Drink water through the day and sip water with meals to help with chewing and swallowing.
• Chew sugarless gum or suck sugarless candies to stimulate saliva. Xylitol-containing products may also help prevent cavities.
• Limit caffeine, alcohol and tobacco, which dry the mouth further.
• Use a humidifier at night, especially if you breathe through your mouth.
• Choose an alcohol-free mouthwash, or one made for dry mouth.
• Clean your tongue daily. A dry tongue collects coating quickly, and removing it reduces the main source of odor.
• Brush with fluoride toothpaste and clean between your teeth, since dry mouth raises cavity risk.

Many people only notice dry mouth on waking. Saliva naturally drops during sleep, and sleeping with your mouth open, snoring, a blocked nose or an evening dose of a drying medicine all make it worse. Cleveland Clinic notes dry mouth at night is more likely to cause cavities. Practical steps:

• Brush, clean between your teeth and clean your tongue before bed.
• Keep water by the bed for sips during the night.
• Run a cool-mist humidifier in the bedroom.
• Skip alcohol and caffeine in the evening.
• Ask your doctor whether a drying medicine can be taken at a different time of day; do not change it yourself.

Treatment depends on the cause. If a medicine is responsible, a doctor may change it or adjust the dose; never stop a prescribed medicine on your own. A dentist or doctor may recommend artificial saliva products or prescribe a medicine that helps the salivary glands make more saliva. Because dry mouth raises the risk of cavities and gum disease, tell your dentist about it so they can watch for problems at checkups.

See a dentist or doctor if your mouth feels dry most of the time, especially if you also have dry eyes (a possible sign of Sjögren's disease), increased thirst and frequent urination (a possible sign of diabetes), or new cavities despite good brushing.