Bad breath

Bad breath happens to everyone at some point, and research suggests that between 25% and 50% of people are regularly affected. Known medically as halitosis, bad breath is best tackled by addressing the cause rather than simply disguising the problem with breath fresheners.

By Wallace Health I Medically reviewed by Adrian Roberts.
Page last reviewed: October 2018 I Next review due: October 2023

Types of halitosis

There are three types of halitosis: 

  • Normal — this includes bad breath:
    • After drinking lots of alcohol
    • After eating certain foods with strong odours eg Brussels sprouts, cabbage, garlic, onions, spices 
    • If you smoke
    • In the morning when you wake up 
    • When fasting or going on a crash diet or low-carbohydrate diet
  • Pathological — when there is an underlying medical problem causing your bad breath eg a problem in your mouth or an illness or medical condition
  • Psychological — when you do not have bad breath but are anxious that you do; halitophobia is an extreme case of psychological bad breath that can be treated with psychological therapy and commonly causes changes in behaviour, such as: 
    • Avoiding other people or staying far away from them
    • Frequently cleaning your teeth and tongue
    • Frequently using chewing gum, mints, mouthwashes and sprays

Causes of bad breath

Most bad breath is due to poor oral hygiene, food or drink, or dehydration, but sometimes it can be a sign of an underlying health problem. The possible causes are wide-ranging and include:

  • Alcohol — this is dehydrating, increases the bacteria linked to gum disease and raises the risk of acid reflux, which is another cause of bad breath
  • Crash dieting and low-carbohydrate diets — this causes your body to rapidly break down fat stores, releasing chemicals called ketones that give off a sweet, sickly smell
  • Diet — some foods such as raw onions, garlic and spices can produce odours after digestion when they enter your bloodstream and reach your lungs
  • Dry mouth — saliva helps keep bacteria under control, so if you don’t produce enough, bacteria will build up
  • Poor oral hygiene — food remaining on or between your teeth is broken down by bacteria, which release unpleasant smells; this can lead to tooth decay and gum disease, worsening the problem
  • Smoking — the chemicals in cigarettes directly cause bad breath as well as damaging gums, increasing the risk of gum disease

Underlying medical conditions can also cause bad breath. These range from short-term infections to long-term or serious problems, such as diabetes.

Talk to your doctor if you’re concerned about symptoms

You can book an appointment with a Spire private GP today.

Conditions related to bad breath

Sometimes, bad breath has an underlying medical cause such as:

  • Diabetes — if diabetes is undiagnosed or poorly controlled, your body can’t break down glucose for energy, so it breaks down fat instead, which causes the production of chemicals called ketones, which have a sweet, fruity odour

  • Infections — this includes infections of the mouth, nose, throat and lungs, such as dental abscesses, bronchitis, sinusitis and tonsillitis 

  • Gastrointestinal conditions — this includes:
    • Acid reflux — when stomach acid leaks back up into your oesophagus (gullet), causing a burning sensation
    • Infection with the bacterium Helicobacter pylori, which increases the risk of stomach ulcers

  • Other causes — this includes:
    • Liver or kidney problems
    • Sjögren’s syndrome
    • Some cancers

How do I tell if I have bad breath?

You may not notice you have bad breath as you will be used to your own smell. One way to find out is to ask a close friend or family member if your breath has an unpleasant smell. Alternatively, you can lick the inside of your wrist, wait for it to dry and then smell the area you licked. If it smells unpleasant, you most likely have bad breath.

Getting a diagnosis for bad breath

If you think you have bad breath, first see your dentist. They can check for signs of tooth decay, gum disease and infections, and can spot signs of some serious conditions such as mouth cancer. They may recommend:

  • A visit to the hygienist who can give your mouth and gums a thorough clean and advise you on dealing with gum disease
  • A visit to your GP who can assess any possible medical cause
  • An X-ray to examine your teeth more closely


To determine possible causes, your GP may ask you about other symptoms you have and look for other causes if your dentist cannot find a cause. This may involve:

  • A gastroscopy — inserting a thin, flexible tube with a camera on the end down your throat to examine your gullet and stomach
  • A nasendoscopy — inserting a thin, flexible tube with a camera on the end to examine the inside of your nose 
  • Blood tests — this will help rule out or diagnose other conditions
  • Getting you to breathe out from your nose and your mouth separately, and then smelling your breath to help determine the cause
  • Helicobacter pylori testing — this may involve a breath, blood or stool test for the germ

Treatments for bad breath

Treatments vary widely, depending on the cause. Here are some of the most common solutions for getting rid of bad breath:

Good oral hygiene routine

This will involve:

  • Brushing twice a day for two minutes at a time
  • Flossing or using an interdental brush once a day
  • Brushing your tongue to remove bacteria daily
  • Using a mouthwash that doesn’t contain alcohol – your dentist can advise
  • Changing your toothbrush at least every three months
  • Going for regular dental hygiene appointments and check-ups

Lifestyle changes may include:

  • Quitting smoking
  • Drinking plenty of water
  • Avoiding too much pungent food and drink such as onions, garlic, spices and coffee
  • Limiting alcohol intake

Other treatments may include:

  • Management or treatment for whatever medical condition is causing your bad breath
  • Changing any medication if your doctor thinks it's causing your bad breath

Frequently asked questions

What causes bad breath even after brushing?

Bad breath even after brushing may be caused by a variety of different medical conditions, including:

  • Diabetes that is undiagnosed or poorly controlled 
  • Gastrointestinal conditions — this includes acid reflux and Helicobacter pylori infection
  • Gum disease or tooth decay
  • Infections of your mouth, nose, throat or lungs
  • Other medical conditions — this includes liver or kidney problems, some cancers and Sjögren’s syndrome

Crash diets or low-carbohydrate diets can also cause bad breath, even after brushing. As a first port of call, see your dentist to find out the cause of your bad breath. If they cannot diagnose the problem, they may refer you to your GP for further examination.

What is bad breath a sign of?

Bad breath is not usually a sign of anything serious and in most cases, is normal. It may occur: 

  • After drinking lots of alcohol
  • After eating certain foods with strong odours eg Brussels sprouts, cabbage, garlic, onions, spices 
  • If you smoke
  • In the morning when you wake up 
  • When fasting or going on a crash diet or low-carbohydrate diet

However, in some cases, bad breath may be a sign of an underlying medical problem, such as an infection of your mouth, nose, lungs or throat, diabetes, or a gastrointestinal, kidney or liver problem. Less commonly, it could be a sign of certain cancers or Sjögren’s syndrome.

If you are concerned about your bad breath, first see your dentist. They may refer you to your GP if they cannot find the cause.

How can I permanently get rid of bad breath?

Most people experience bad breath at some point in their lives and in most cases, this is normal. However, if you have persistent bad breath, even with good oral hygiene, you may have an underlying medical condition (eg acid reflux, Helicobacter pylori infection, uncontrolled or undiagnosed diabetes), which will need treatment to get rid of your bad breath. The treatment will depend on the specific cause of your bad breath. See your GP to get a diagnosis and receive appropriate treatment.

Can bad breath come from your lungs?

Yes, bad breath can come from your lungs if you have a lung infection. This can cause inflammation and the production of phlegm or pus in your lungs. Coughing up the phlegm or pus can cause bad breath.


What does a rotten tooth smell like?

A rotten tooth, or tooth decay, causes a foul smell, sometimes described as a rotten egg smell. Tooth decay is a serious condition and you should see your dentist for treatment.

What foods help with bad breath?

Foods rich in vitamin C protect your gums and mouth from bacteria that release chemicals, which cause bad breath. Chewing sugar-free gum can also combat bad breath as this increases the flow of saliva in your mouth to help clear out food debris. Similarly, drinking water helps clear out food debris and also increases saliva production.