The scientific name for Bad Breath is Halitosis, and the dictionary definition of Halitosis, taken from The Oxford Paperback Dictionary is "breath that smells unpleasant".
Bad breath is usually caused by bacteria which live on the coating on the gums and teeth in your mouth and when not removed properly the food particles left behind are changed into sulfuric gases by these bacteria, resulting in the unpleasant smell when we breathe out. It should be noted that bacteria do not actually live on the tongue or teeth and gums but on a coating on them and if the coating is continually removed by proper oral dental care then the bacteria will not build up.
A popular remedy is the use of a mouthwash, peppermint and spearmint flavours being in abundance, some of these can be quite strong, and leave the mouth with a tingling feeling afterwards. Mouthwashes are just that and should not be swallowed.
If you run out of mouthwash or just don't like it, then you could try real lemon, just squirt a drop or two in your mouth, rinse it around and then, in this case, it is safe to swallow it.
Another idea to stop bad breath is the use of Heinz Apple cider vinegar. Use an ordinary glass and mix equal amounts of the vinegar and water and use it as a mouthwash. Vinegar is acetic acid which lowers the PH level in your mouth and so the bacteria which produce the smell are then destroyed.
If you have any Alka Seltzer stored away in your cupboards then this is an old bad breath remedy, by dissolving a couple of tablets in warm water and using the mixture as a mouthwash the PH levels in your mouth go down and the bacteria is killed.
If you are out on the town and worried about bad breath there is always the old faithful credit card, just scrape your tongue with the edge of the card and remove the odour producing bacteria as you do it, not a cure but it may just get you by for the evening.
With the right cleaning regime bad breath can be cured and kept at bay, all toothbrushes should be replaced regularly at least every 3 months. Don't just brush the teeth but brush the gums as well and buy a tongue brush and clean that too and bad breath will be a thing of the past.
Most toothpaste contains a substance called sodium laryl sulphate which is a foaming agent and may dry the mouth out, this helps bacteria rather than being detrimental to them, it is advisable to find a toothpaste without that ingredient. Using one with chlorine dioxide would be the better choice.
There can be other causes of bad breath than just the bacteria in the mouth from food. Chronic bad breath can be a result of an illness, syphilis, taking antibiotics or other medication, also smoking, or vomiting.
Bad breath can be covered up by chewing gum or sucking mints and boiled sweets, but it is only a temporary thing and the cause of continual bad breath should be investigated further, if it is not cured by the above methods and good dental regime.