Bad breath is caused by bacteria
In most cases the source of the unpleasant smell is intraoral and is to be found in the mouth itself.
Hardly anyone talks about bad breath – many are affected by it. The technical term is halitosis, and in the great majority of cases it arises not in the stomach, as is often assumed, but in the mouth itself.
Where the smell arises
Bacteria that break down protein residues are responsible. In doing so they produce sulphurous compounds – the same ones that give rotten eggs their smell. They gather above all on the back of the tongue, between the teeth and in periodontal pockets.
The connection with the gums
That is precisely why persistent bad breath is a warning sign: deep pockets offer bacteria a sheltered space that the toothbrush does not reach. Anyone affected regularly and without obvious cause should have the periodontium examined rather than simply reaching for chewing gum.
If treating the cause helps, the smell disappears. Mouthwashes only mask it.