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Bad breath is an unpleasant smell on your breath. Other people may notice it when you speak or breathe out. You might not be aware of it yourself.

Everyone gets bad breath occasionally, but some medical problems can mean you have it most of the time or even all of the time. Bad breath is sometimes called halitosis.

Lots of people have bad breath first thing in the morning. That's because saliva usually keeps your mouth clean, and it dries up while you sleep.¹

"Morning breath" is probably worse in people who tend to breathe through their mouths rather than their noses.² But the problem is easily put right. It will go away as soon as you have something to eat, brush your teeth or rinse your mouth.

You can also have temporary bad breath after:²

• Eating spicy or strong-smelling foods, like garlic, raw onions or chilli
• Smoking
• Drinking alcohol.

Most people put up with bad breath for a little while if they enjoy these things. But steering clear of alcohol, cigarettes or spicy food can help you avoid bad breath.

Bad breath that lasts through the day is usually caused by a problem in your mouth.³ For 9 in 10 people, bad breath is caused by either gum disease or bacteria that grow on your tongue.^{1 3}

However, bad breath is occasionally caused by a medical problem somewhere else in your body. Conditions that can cause bad breath include sinusitis, tonsillitis, and some lung problems or stomach problems.

Here are the different types of bad breath.⁴

Bacteria can grow on the coating on the back part of your tongue. As they grow, bacteria give off gasses. These gasses can make your breath smell bad.

You may be more likely to have this kind of bad breath if you:⁵

• Smoke
• Don't brush your teeth every day
• Don't produce enough saliva.

Not producing enough saliva can be a problem because saliva helps to keep your mouth clean. You might produce less saliva than usual if you:

• Are taking some medications, such as antihistamines, antidepressants or pills for high blood pressure
• Have problems with the glands in your mouth that make saliva
• Don't drink enough water
• Don't eat regularly enough
• Breathe through your mouth too much.

The most common problem that causes bad breath is gum disease. You get gum disease because of plaque. Plaque is a coating on your teeth. It's mainly made up of bacteria. These bacteria can sometimes infect your gums and make them inflamed.

There are two main stages of gum disease.⁶

• Gingivitis. This is when your gums become red and swollen. They may bleed easily when you brush your teeth. You can get rid of gingivitis by brushing your teeth at least twice a day. Flossing can also help, by getting rid of plaque from between your teeth. Or you can get your teeth thoroughly cleaned by a dentist or dental hygienist.
• Periodontitis. This is a later stage of gum disease. Your gums start to pull away from your teeth and form pockets that are infected. If you don't get treatment, the bones, gums and other tissue that support the teeth can be destroyed. If this happens, teeth may eventually become loose and have to be removed.

Other problems in your mouth that can cause bad breath are:²

• An infection in the tooth socket after a tooth has been taken out
• Canker sores
• Bits of food that collect under something in your mouth, such as braces or a bridge.

Bad breath can be caused by a condition that affects your throat, lungs or somewhere else in your body. Conditions that can cause bad breath include:^{1 2 7}

• Sinusitis. This is an infection of the air spaces behind your nose
• Bronchitis. This is an infection in your airways
• Tonsillitis. This is a type of throat infection
• A blocked nose that lasts a long time
• An object that's trapped in your nose. Children sometimes put small objects in their noses
• Diabetes. If you have diabetes, your body may burn fat for energy instead of glucose. This is called diabetic ketoacidosis. It can make your breath smell fruity or sweet. Diabetic ketoacidosis is very serious. Anyone who has it should see a doctor right away
• Problems with your digestive system. For example, heartburn can make stomach acid and gas travel back up into your throat
• Liver or kidney problems
• A condition called trimethylaminuria. This happens when a chemical called trimethylamine can't be broken down by your body. Instead, you get rid of it in sweat and saliva. This causes bad breath and body odor.

Some people worry that they have bad breath when they actually don't. This is called pseudo-halitosis. People with pseudo-halitosis tend to look for signs in other people's behavior to prove to themselves that their breath is bad.²

Some people with pseudo-halitosis continue to worry that they have bad breath even after they've been examined and reassured. This is sometimes called halitophobia. A phobia is when you're very afraid of something.

Thinking you have bad breath can be very upsetting.⁸ It's even been known for people with halitophobia to commit suicide.

A doctor or dentist can help you with bad breath. If your problem is caused by bacteria or a problem in your mouth, your dentist will be able to suggest treatment. Your dentist will also be able to offer advice if you think you have bad breath but it turns out you don't.⁴

If your bad breath is caused by a medical condition somewhere else in your body, you'll need to see a doctor. If you have halitophobia, and you feel bad about your breath even though nothing is wrong, your doctor may arrange for you to see a therapist or counsellor who can help you.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.