Bad breath causes

Last Updated September 2023

Halitosis (Bad breath): Causes and Treatment

Chronic bad breath, or halitosis, is caused by the build-up of bacteria in the mouth, which then produces a bad smell. Short-term bad breath after eating certain foods and everyday ‘morning breath’ are not halitosis. Instead, halitosis symptoms include a persistent bad smell in the mouth that is not alleviated by brushing, flossing, or using mouthwash.

Bad breath can be embarrassing, but it’s also common and treatable. In fact, there are many ways that you can freshen breath at home. However, persistent bad breath symptoms could indicate an underlying health condition and should be discussed with your dentist.

In this article, we’ll cover the causes of bad breath and explore some ways you can keep your mouth fresh.

In this article:

Common causes of bad breath

There can be many causes of bad breath, and most come down to your lifestyle choices, dental hygiene habits and, of course, what you put in your mouth. When a regular routine of brushing, flossing, and rinsing isn’t enough to combat your bad breath, it could be time to ask yourself some tough questions regarding your lifestyle and habits.

Here are some common causes of bad breath:

Poor dental hygiene

With all the food and drink you consume in a day – from sugary cereals to tea-time takeaways – it’s important that you brush and floss daily. Everything you eat is broken down in your mouth, so food particles can remain in there, trapped on teeth, gums and on your tongue. Doing a thorough job of getting rid of these can help to stop bacteria growing in your mouth, which can eventually cause bad breath.

What you can do:

• Brush twice a day.

• Use an antibacterial mouthwash like LISTERINE® Total Care. Mouthwash flavours like LISTERINE® Cool Mint can also provide lasting fresh breath confidence.

• Try fluoride toothpaste.

• Don’t forget to floss.

• Clean your tongue.


The natural bacteria in your mouth absolutely love turning sweet treats into unpleasant smells, and acidic foods create an optimum environment for these bacteria to carry on growing. Without carbohydrates, your body starts breaking down other fats and proteins for energy, producing an odorous breath that is anything but fresh.

Foods to avoid:

Garlic – Although it tastes good, and no Saturday night is complete without a few slices of cheesy garlic bread, too much of it can cause bad breath – and brushing tends to just cover up the smell temporarily. Garlic is absorbed into your bloodstream, enabling a wave of odour to make its way into your lungs, where it can freely escape through the mouth. None of this, however, should be reason to swear off garlic completely. The odour should dissipate once all that garlicky goodness has been digested. Just remember to brush, floss, and use LISTERINE® mouthwash twice daily.

Onions – Onions, like garlic, are lingerers. They both contain sulphuric compounds that get absorbed into your bloodstream and return when you least expect it. You can help combat the lingering odour by practising good dental hygiene, brushing after you eat with fluoride toothpaste, or even just rinsing out your mouth straight after with water (if there’s no mouthwash to hand).

Acidic foods - The bacteria that cause bad breath thrive on the acidic environment resulting from low pH foods such as lemons, oranges, and tomatoes. Our advice – eat these things in moderation.


It’s not just food that can leave a nasty smell, in your mouth. For example, the more often you raise your glass, the more you raise your chances of bad breath. That’s because alcohol not only causes dry mouth, but it can also allow bacteria to linger after you finish drinking.

Coffee is also another bad breath bringer. It may be your morning treat, but the caffeine in coffee reduces saliva production in your mouth. Less saliva means an increase in bad breath-causing bacteria. It also means any food particles that may linger from your last meal start to break down inside your mouth.

What you can do:

Drink plenty of water to help prevent dry mouth.

Eat your fruit and veg – apples and carrots are just a few examples of fruits and vegetables that can help clear away excess bacteria.

Practice good dental hygiene – this includes brushing with a fluoride toothpaste at least twice a day, flossing and using LISTERINE® mouthwash at least once a day.


Some of the main side effects of smoking are halitosis and less-than-healthy gums. Not only can tobacco encourage gum inflammation, but this can also lead to gum disease. Besides the tobacco smell on your breath that comes with smoking, gum disease itself can also cause bad breath – along with bacteria build-up, bleeding, and enamel decay.

How can you combat gum disease?

• Regular teeth brushing.

• Flossing.

• Rinsing with a mouthwash like LISTERINE® Advanced Defence Gum Treatment to help form a protective shield to prevent plaque germs attaching to your gums.

• Getting regular dentist check-ups.

Dry mouth

Xerostomia, otherwise known as dry mouth, usually occurs when the production of saliva slows down and, in persistent cases, it can also lead to bad breath. Saliva is actually incredibly important – it flushes away bacteria and leftover food that are otherwise happy to hang around in your mouth. When your saliva dries up, that means there’s nothing to stop those bits and pieces from building up and creating an unpleasant odour.

How to avoid dry mouth

• Drink plenty of water.

• Suck on ice cubes or ice lollies.

• Chew sugar-free gum.

• Sip on cold, unsweetened drinks.

Acid reflux

Acid reflux, or gastroesophageal reflux disease, and certain gastrointestinal problems can all cause stomach acid and contents from your stomach to re-enter your mouth, leading to bad breath. In some cases, acid reflux can come as a result of certain factors, including:

• Being overweight.

• Eating and then lying down or going to bed straight after.

• Alcoholic, carbonated and caffeinated drinks.

• Smoking.

• Eating citrusy, acidic, and garlicky foods.

How to avoid reflux

• Maintain a healthy weight.

• Eating a few hours before lying down.

• Eating smaller meals and changing the types of food you eat.

• Quitting smoking.

• Seeing a doctor to help find the root cause of your acid reflux.


If your dentures aren’t properly cleaned, this can lead to a build-up of food and bacteria, which can then cause bad breath.

How to keep your dentures clean

You should rinse your dentures and brush away food particles and debris twice a day using warm water, a brush and mild soap.

How to combat bad breath

There are plenty of easy steps to try and combat bad breath at home. However, you should visit your dentist or doctor if you’re concerned about any persistent bad breath.

So, how can you combat bad breath at home?

Practice good oral hygiene

If you’re battling bad breath without success, it could be the fault of your routine. Ask yourself “am I brushing, flossing, and rinsing regularly?” If the answer is no, this might be a good place to start.

Here are some things you might want to consider incorporating into your daily oral hygiene routine :

Use an antibacterial mouthwash – such as LISTERINE®, to help remove unwanted smelly bacteria and keep your breath smelling fresh. LISTERINE® Total Care kills up to 99% of the plaque and bad breath causing germs left behind after brushing.

Brush regularly – gently brush your teeth at least twice a day for two minutes to remove bacteria and food particles, which can contribute to bad breath.

Gently clean your tongue once a day using a scraper or cleaner – Remember to give the tongue a little attention, as it may be loaded with decaying food particles and bacteria that cause bad breath.

Get regular dental check-ups

Seeing your dentist regularly is important when spotting signs of decay, infections, or gum problems. You might find that you’ve been practising great oral hygiene, but you’re still stuck with persistent bad breath – this is why your dentist is so important.

Not only will your dentist give your teeth an expert touch, but they can also conduct an oral exam to detect and treat periodontal disease and other problems. They can also refer you to a doctor to help determine the cause of bad breath if it’s not due to an oral cause.

Stay hydrated

Drinking water helps flush away excess food and bacteria, and it also keeps your tongue and mouth moist, thus preventing dry mouth – a possible factor contributing to your bad breath. Remember to steer clear of fizzy drinks – all that excess sugar will bind to your teeth and gums, mixing with the leftover remnants of your meal and contributing to bad breath.

Quit smoking

Without getting into some of the more serious side effects of tobacco use, smoking will – at the very least – give you smoker’s breath. Smoking also contributes to developing gum disease.

As with any addiction, quitting can be much more difficult than expected. So, talk to your doctor or pharmacist about beating the habit.

Keep your dentures clean

Keeping your dentures clean is key to keeping your mouth clean. Unclean dentures can lead to bad breath and other complications, including gum disease and oral thrush. To make sure you’re doing a good job and getting rid of all the bacteria and food deposits, brush your dentures with toothpaste or soap and water before soaking them in a solution of denture-cleaning tablets and water. Once done, brush them again just as you would with your teeth – and do this at least twice a day. For extra protection, rinse your mouth out with LISTERINE® mouthwash every day.

Chew sugar-free gum

Chewing sugar-free gum after you eat can help freshen up your breath and keep saliva flowing, so your mouth can naturally flush out bacteria and food particles.

Don’t chew too much non-sugar-free gum, as this can increase your chances of tooth decay. The sugar will also stick to your teeth and add to your problem. Chewing too many mints should also be avoided. At best, they just mask bad breath and are also loaded with sugar.

Know when to consult a medical professional

If you have persistent bad breath that won’t go away after you’ve improved your oral hygiene and tried treating it yourself, you should see a dentist or doctor. Other symptoms you should seek advice on include:

• Denture problems – especially if they don’t fit right.

• Swollen, painful or bleeding gums.

• Loose adult teeth.

• Toothache.

Bad breath: Frequently Asked Questions

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