Researchers have isolated bacteria which can grow on and destroy some of the compounds that cause bad breath.
Bacteria can fight bad breath
The King's College London research, in Environmental Microbiology, could help develop a natural way to beat halitosis and other odours such as smelly feet.
The compounds behind bad breath are produced when sulphur-containing amino acids break down in the mouth.
Odour-eating methylotrophic bacteria were isolated from the tongue, tooth plaques and gum edges of volunteers.
Until now it was not recognised that these bugs were a normal part of the microbial environment inside the mouth.
The King's team found no difference between strains of bacteria found in the mouths of healthy volunteers and those suffering from periodontitis - a form of gum disease often associated with smelly breath.
However, the researchers suspect people who suffer from bad breath may have lower levels of the bacteria.
The King's team has previously shown that methylotrophic bacteria are found on the feet - where sulphur derivatives can also cause odours.
Lead researcher Dr Ann Wood told BBC News it might be possible to combat bad breath by modifying mouthwashes and toothpastes to enhance the activity of methylotrophic bacteria.
She said levels of mouth bacteria varied depending on a number of factors, including gum and liver disease, smoking and diet.
"If concentrations of the smelly compounds are high (as in bad breath) the number of methylotrophs would also be expected to rise, but as these compounds are toxic this would potentially limit the bacterial activity.
"Poor oral hygiene will lead to accumulation of material between teeth, coating the tongue and plaque deposition, all of which are likely to raise the output of the relevant compounds."
Dr Phil Stemmer, of the Fresh Breath Centre in London, said the theory sounded promising.
However, he said it was not just a case of increasing levels of potentially beneficial bacteria - they would have to replace other types of bacteria in the mouth that caused bad breath by breaking down amino acids.