Bad breath: causes and how to fix it

Reviewed by Dr. Samar Fadavi, DDS

Short answer: Most bad breath starts in the mouth, from bacteria on the back of the tongue, between the teeth and under the gums. Brushing twice a day, cleaning between the teeth, gently cleaning the tongue and drinking enough water usually help within days. Breath that stays bad despite good care needs a dental exam to look for gum disease, decay or another cause.

What causes mouth odour, and how do you get rid of it?

Almost everyone has bad breath at some point. Morning breath, garlic at lunch, a strong coffee before a meeting: these are normal and pass. Persistent mouth odour is different. It lingers through the day, comes back soon after brushing, and can make people self-conscious at work, with family or when meeting someone new. The medical name is halitosis.

The reassuring part is that in most people the cause is found in the mouth and can be dealt with. This guide explains where the smell comes from, a daily routine that helps, the habits that make it worse, and the signs that mean it is time for a dental visit. It is general information, not a diagnosis.

Where bad breath comes from

Bacteria on the tongue

The top surface of the tongue is rough, with many tiny folds. Toward the back, where it is hard to reach, bacteria, food debris and dead cells collect in a whitish or yellowish coating. As these bacteria break down proteins, they release sulphur compounds that smell unpleasant. In many people with ongoing bad breath, the tongue coating is the main source.

Plaque between the teeth and along the gums

Food trapped between teeth and plaque at the gumline also feed odour-producing bacteria. If you notice a smell on your floss after cleaning between certain teeth, that area is likely contributing.

Gum disease

When gum inflammation progresses to periodontitis, pockets form between the teeth and gums. These pockets are low in oxygen, which suits the bacteria that produce the strongest odours. Bad breath with bleeding gums, receding gums or loose teeth is a common pattern. Our guide on bleeding gums explains the early stage.

Tooth decay and broken fillings

A large cavity, a cracked filling or the edge of an old crown can trap food and bacteria in a spot no brush can reach. An infected tooth can also cause a bad taste.

Dry mouth

Saliva rinses the mouth and keeps bacteria in check. When saliva flow drops, odour rises. That is why breath is worst first thing in the morning. A dry mouth during the day can come from breathing through the mouth, not drinking enough water, alcohol, smoking, and hundreds of common medications, including some for blood pressure, allergies, depression, anxiety and bladder control. Dry mouth is especially common in older adults.

Dentures, bridges and appliances

Dentures, partial plates, retainers, night guards and aligners collect plaque and food just like teeth. If they are not cleaned every day, or are worn overnight without a break, they can hold a strong smell.

Food, drink and tobacco

Garlic, onions and some spices are absorbed into the bloodstream and released through the lungs, so brushing only masks them until they pass. Coffee and alcohol dry the mouth. Smoking and vaping leave their own odour, dry the tissues and raise the risk of gum disease.

Causes outside the mouth

Less often, bad breath comes from the nose, sinuses or throat: post-nasal drip, sinus infections and tonsil stones (small, pale, smelly deposits in the folds of the tonsils). Acid reflux, uncontrolled diabetes, kidney or liver conditions and very low-carbohydrate diets can also change breath. If the mouth is healthy and the odour continues, your family doctor is the next step.

A daily routine that helps, step by step

1. Brush twice a day for two minutes. Use a soft brush and fluoride toothpaste, angling the bristles toward the gumline.
2. Clean between your teeth once a day. Floss, interdental brushes or a water flosser all work. Pay attention to areas where food tends to catch.
3. Clean your tongue. Use a tongue scraper or the back of your toothbrush. Start as far back as is comfortable and draw forward gently, five or six times. Rinse the scraper between passes.
4. Drink water through the day. Sip regularly, especially if you talk a lot for work, exercise, or take medications that dry the mouth.
5. Chew gum without sugar after meals. Chewing stimulates saliva. Choose a gum sweetened with xylitol or another sugar substitute.
6. Clean appliances every day. Brush dentures and plates with a denture brush and soak them overnight in a cleanser made for them. Rinse aligners and night guards and brush them gently with cool water.
7. Choose a rinse carefully. A rinse without alcohol is kinder to a dry mouth. Rinses that only mask odour wear off quickly; ask us about antibacterial options if you need one.
8. Keep up with cleanings. Tartar under the gums cannot be removed at home. Regular professional cleanings remove it before it causes trouble.

What to avoid

• Covering the smell instead of treating the cause. Mints, sprays and strong rinses hide odour for minutes. If you rely on them all day, something needs attention.
• Mints and candies with sugar. They feed the bacteria that cause decay and odour.
• Rinses high in alcohol if your mouth is dry. They can dry the tissues further.
• Skipping breakfast. Eating stimulates saliva and helps clear morning breath.
• Sleeping in dentures. Give your gums a rest overnight and soak the denture, unless your dentist has advised otherwise.
• Scraping the tongue too hard. Gentle strokes are enough. Scraping until it hurts can irritate the surface.

How to tell whether your breath is the problem

It is hard to judge your own breath because the nose gets used to familiar smells. A few simple checks can help. Lick the inside of your wrist, let it dry for a few seconds and smell it. Or gently scrape the back of your tongue with a clean spoon and smell the coating. Better still, ask someone you trust to tell you honestly. Some people worry a great deal about breath that others do not notice. If that sounds familiar, an exam can reassure you as well as find any real cause.

How bad breath is assessed at the clinic

At an exam, the dentist checks your teeth, fillings and crowns for places that trap food, measures the spaces between the teeth and gums, looks at the tongue, and asks about medications, dry mouth, reflux and sinus problems. X-rays may be taken to look for decay between teeth or below fillings. Most people leave with a clear explanation of where the odour is coming from and a plan.

Depending on what is found, the plan may include a professional cleaning, treatment for gum disease, repairing a broken filling or crown, managing dry mouth, or a referral to your family doctor if the cause seems to lie outside the mouth. A routine visit is described on our check-ups and family dentistry page.

Bad breath at different ages

Children

In young children, bad breath often comes from mouth breathing, a blocked nose, large tonsils or food caught between back teeth. Occasionally a small object in the nose is the cause, especially if the smell comes with discharge from one nostril. If a child’s breath stays bad, see the dentist and the family doctor. Our children’s dentistry page explains how we care for young patients.

Teens and adults with braces

Brackets and wires trap food. Interdental brushes and a water flosser make cleaning easier, and a quick rinse after lunch helps.

Older adults

Dry mouth from medications, dentures and gum recession make bad breath more common later in life. Daily denture care, water through the day and regular cleanings make a noticeable difference. Our page on dental care for seniors covers how we help.

Common myths about bad breath

“If I brush harder, it will go away.” Brushing harder wears the gums and enamel without reaching the main sources, which are the back of the tongue, the spaces between the teeth and pockets under the gums. Gentle, thorough cleaning in the right places matters more than force.

“Bad breath always comes from the stomach.” Reflux can play a part, but in most people the cause is in the mouth. That is why a dental exam is usually the first step, and the family doctor the second if the mouth is healthy.

“Mints mean my breath is fine.” Mints and sprays only hide odour for a short time, and those with sugar feed the bacteria that cause decay. If you need them all day, the cause has not been dealt with.

“Only people who skip brushing have bad breath.” Careful brushers can still have odour from a dry mouth, medications, a coated tongue, an old filling that traps food, or tonsil stones. Bad breath is not a sign that someone is careless.

“Dentures cannot cause bad breath because they are not real teeth.” Denture material collects plaque and food just like natural teeth. Daily brushing and an overnight soak keep it clean, and a denture that no longer fits well can trap more debris.

“Nothing can be done about dry mouth.” A great deal can be done. Sipping water, chewing gum without sugar, a humidifier at night, saliva substitutes and a medication review with your doctor or pharmacist can all help. We can suggest products that protect the teeth when saliva is low.

Small changes that make a big difference

Keep a tongue scraper next to your toothbrush so it becomes part of the routine. Carry a small water bottle during the day. If you work long shifts, brush or rinse after lunch. Set a reminder to replace your toothbrush every three months. Ask us to show you how to reach the back teeth and the gumline more easily; a small change in brush angle often helps more than a new product.

When to see a dentist

Book an exam if:

• Bad breath continues after two weeks of careful brushing, cleaning between the teeth and tongue cleaning.
• You also have bleeding, swollen or receding gums.
• You have a bad taste that does not go away, or a tooth that hurts.
• A filling or crown is broken, or food keeps catching in one spot.
• Your mouth often feels dry.
• Your dentures smell even after cleaning, or no longer fit well.

Call promptly if you have facial swelling, a painful lump on the gum or a fever with tooth pain. These can be signs of an infection, and our same-day emergency care page explains how to reach us.

Questions about bad breath

Why is my breath worse in the morning?

Saliva flow drops during sleep, so bacteria multiply. Mouth breathing and snoring make it worse. Brushing, cleaning your tongue and eating breakfast usually clear it.

Does mouthwash fix bad breath?

Mouthwash can freshen breath for a short time and some types reduce bacteria, but it does not remove plaque or tartar. It works with brushing and cleaning between the teeth, not instead of them.

Can a tooth that needs a root canal cause bad breath?

An infected tooth can cause a bad taste or odour, especially if it drains into the mouth. Our root canal treatment page explains how infected teeth are treated.

What are tonsil stones?

They are small, pale deposits that form in the folds of the tonsils and can smell strongly. Gargling and good oral hygiene help. If they are frequent or uncomfortable, see your family doctor.

Can diet cause bad breath?

Yes. Strong foods such as garlic and onions affect breath for hours. Very low-carbohydrate diets can produce a distinctive smell as the body burns fat. Drinking water helps.

Is tongue scraping safe?

Yes, when done gently. Use a scraper or soft brush, start toward the back, and use light pressure. Stop if it causes pain or bleeding.

Can stress or anxiety cause bad breath?

Stress can dry the mouth and change routines, both of which affect breath. Some people also become very anxious about breath that others do not notice. An exam can help either way.

Related guides

• Salivary glands and saliva explained
• Dry mouth and medications after 60
• Oral piercings and your teeth