What causes bad breath

‘Morning breath’

Almost everyone has bad breath first thing in the morning. During the day, movement of the tongue and cheeks dislodges food debris and dead cells, and these are washed away by saliva. While we are asleep our tongue and cheeks do not move much, and the flow of saliva is reduced. The food residues stagnate in the mouth, and mouth bacteria rapidly break them down, releasing an unpleasant stale smell. Breathing through the mouth when sleeping tends to make this worse. Fortunately, morning breath normally disappears after breakfast, cleaning the teeth or rinsing the mouth with water. Get your saliva going with a drink of water and lemon.

Temporary bad breath

Temporary bad breath is the lingering effect of cigarettes or something you have eaten or drunk in the past 24–48 hours. Alcohol, onions, cabbage, broccoli, radish, durian, garlic, curries and other highly spiced foods, cured foods such as salamis, and smoked foods such as kippers are particularly likely to remain on the breath. The problem isn-t simply that the smells stay in the mouth. These foods are digested and then broken down in the body, and the breakdown products of some, particularly alcohol, onions and garlic, are expelled in the breath for hours or days afterwards (this is the basis of the breathalyser test for alcohol).

Smoking also reduces the flow of saliva, which makes its smell linger even longer.

Traditional remedies such as eating parsley help, and mouth fresheners disguise the smell. Clean your mouth by rinsing it thoroughly with warm water, giving it a good brushing with toothpaste and then rinsing thoroughly again.

Bad breath can even result from not eating. When no food is available, the body starts breaking down fat. Waste products from fat breakdown, called ketones, are expelled in the breath, and smell like stale apples.

Persistent bad breath

Gum disease, according to dentists, is the usual cause of persistent bad breath. You will probably be unaware you have the problem because gum disease is not necessarily painful. The gum is likely to bleed when you brush your teeth. It will look very red, but goes pale for a moment if you press on it, and will be slightly swollen where it meets the teeth. Gum disease is caused by plaque, the sticky film of bacteria that naturally forms on the teeth of everyone every day. These bacteria tend to lodge between the teeth and where the teeth meet the gum. The waste products of the bacteria have a foul, stale smell. Apart from bad breath, gum disease can eventually cause loosening of the teeth.

Poor oral hygiene is an obvious cause. If you don't clean your teeth, you will soon develop bad breath.

Postnasal drip can cause bad breath. This is mucus that trickles down the back of the throat. The reason is inflammation in the air passages behind the nose because of allergies or a sinus infection. It often causes a ticklish cough, particularly when lying flat at night. This type of bad breath is worst when the person is speaking.

Bacteria on the back of the tongue are one of the commonest causes of bad breath. Food particles, postnasal drip and stagnant saliva build up in the 'fur' at the back of the tongue, providing a breeding ground for bacteria. These bacteria produce many nasty-smelling chemicals.

Anything that dries the mouth makes bad breath worse, because saliva cleanses the mouth. Tricyclic antidepressant drugs (such as amitriptyline) reduce saliva. Alcohol, alcohol-containing mouthwashes, heavy exercise and fasting can all result in a dry mouth and worsen a bad breath problem.

Isosorbide dinitrate, a drug for angina, sometimes produces an objectionable smell in the mouth.

Gut problems used to be blamed, and enemas and laxatives were often given as cures, but in fact these have very little to do with bad breath. Your stomach is shut off from your throat and mouth by a tight ring of muscle at the base of the foodpipe, so it is normally a closed tube. Therefore no odour escapes from the stomach, except if you belch, or regurgitate food (vomit).

Chest problems, such as obstructive airways disease (chronic bronchitis), can cause bad breath.

Bad breath in a small child may mean that the child has inserted a small object (e.g. a seed or small toy) into the nose, where it has stuck and caused an infection. For this reason, small children with bad breath should be seen by a doctor.

Written by: Dr Margaret Stearn
Edited by: Dr Margaret Stearn
Last updated: Friday, February 12th 2010

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Comments on this article

Posted by Optional on 16/07/2010 at 07:20:28 pm

A friend used to have very bad breath. She had her wisdom teeth out and the bad breath dissappeared. Now about 15 yrs. later, she has bad breath again. It smells like garlic. This is just about 10:00 in the morning after getting ready to go out. She has not eaten garlic!

Posted by Optional on 24/06/2010 at 12:01:26 pm

Thanks for a detail response. I see my problem. I'm on andi depressants, Taking Welbrotrin 150 extented. I never had BAD, BAD breath or dry mouth til I started on andidepreesants. Thanks again.

Posted by Anonymous on 19/06/2009 at 03:06:00 pm

When I open my mouth to speak some of my companions keep rubbing thier noses, to show their digust of the bad-breath smell, I think. Can this be taken seriously as evidence of having bad breath?

Posted by ola on 19/05/2009 at 01:03:00 am

boots used to have these mint tablets you could swallow, what are they called so I may order online?

Posted by someone on 07/04/2009 at 09:13:00 pm

my sister has bad breathe. shes had bad breathe for ages now. It might be bactaria on the back of the tongue, because im almost certain its nothing else but, then again, it might not be. is there any different colours shown on the tongue if it is? because her tongue is very yellow at the back. or is that normal? I want to find out the cause :S