Bad breath (halitosis)

Bad breath, medically called halitosis, is an unpleasant smell coming from your mouth that can be noticeable to yourself or, more often, to people around you. It's very common, thought to affect around 1 in 4 people regularly, and is usually easy to improve once you know the cause.

Symptoms of bad breath

The main symptom is an unpleasant breath odour, which can vary depending on what's causing it. You might notice, or be told, that your breath smells:

• sour or like rotten eggs, from sulfur compounds produced by bacteria
• sweet or fruity, which can be linked to diabetes
• fishy or like ammonia, sometimes linked to kidney problems
• musty, sometimes linked to liver problems.

It's difficult to smell your own breath, so it's often more reliable to ask someone you trust than to try to judge it yourself. A persistent bad taste in your mouth is also a good sign that your breath probably smells too.

Causes and risk factors

In around 9 out of 10 cases, bad breath starts in the mouth itself. The most common cause is poor oral hygiene. Leftover food particles and a build-up of bacteria, particularly on the back of the tongue, break down proteins and release unpleasant-smelling gases.

Other causes can include:

• problems with your teeth or gums, such as gum disease, tooth decay or infection
• a dry mouth, since saliva normally helps rinse away bacteria and food debris
• smoking, which dries out your mouth and increases your risk of gum disease
• eating or drinking strong-smelling foods such as garlic, onions or coffee, or alcohol
• fasting or crash dieting, which changes how your body breaks down fat.

Less often, bad breath comes from elsewhere in the body. Tonsil stones, sinus or throat infections, and conditions such as acid reflux (GORD), diabetes, or kidney or liver disease, can all cause distinctive-smelling breath. Some medicines, including certain blood pressure drugs and antihistamines, cause dry mouth as a side effect, which can also contribute.

Types of bad breath

Doctors sometimes describe bad breath as genuine or non-genuine. Genuine halitosis is bad breath that others can detect, while non-genuine cases happen when someone is convinced their breath smells bad, even though other people can't notice anything. This is sometimes called halitophobia.

Genuine bad breath is also classified by where it comes from:

• intra-oral halitosis, starting in the mouth, which accounts for around 9 in 10 genuine cases
• extra-oral halitosis, coming from elsewhere in the body, such as the nose, throat, lungs or, rarely, a condition affecting the whole body.

Bad breath can also be temporary, for example after eating garlic or first thing in the morning, or persistent (chronic), which is thought to affect around a quarter of people to some degree.

Diagnosing bad breath

The first thing to do is see a dentist. They will examine your teeth, gums and mouth, and may smell your breath directly to help identify the likely source. If they find advanced gum disease, they may refer you to a specialist called a periodontist.

If your dentist can't find a cause in your mouth, they may refer you to your GP, who can look for other possible causes, such as a sinus problem or a condition affecting your digestion.

Treating bad breath

Treatment depends on the cause, but for most people, improving oral hygiene is enough:

• brush your teeth and gums gently for 2 minutes, at least twice a day, using a fluoride toothpaste
• clean your tongue once a day with a tongue scraper or cleaner
• clean between your teeth with floss, interdental brushes or a water flosser at least once a day
• get regular dental check-ups, and keep dentures clean and out of your mouth overnight
• try an antibacterial mouthwash, ideally alcohol-free, rather than one that only masks odours.

It also helps to avoid smoking, cut down on alcohol and drink plenty of water to keep your mouth moist, especially if a dry mouth is contributing to the problem. Sugar-free gum or mints after strong-smelling food can help temporarily, though the smell won't fully clear until the food has left your system, which can take up to 3 days.

If your dentist rules out a dental cause or if you have other symptoms alongside your bad breath, such as heartburn or a blocked nose, your GP can look into whether an underlying condition, such as acid reflux, a sinus problem or diabetes, needs treating instead.

When to see a dentist or doctor

See a dentist if your bad breath doesn't go away despite a few weeks of trying to treat it yourself or if you have painful, bleeding or swollen gums, toothache, wobbly adult teeth or problems with your dentures.

See your GP if your dentist has ruled out a dental cause and your bad breath continues, particularly if you also have symptoms such as heartburn or a chronic blocked or runny nose, since these can point to a cause elsewhere in the body that needs its own treatment.