It’s common knowledge that alcohol can kill bacteria (it’s commonly used as a disinfectant), so it makes sense that the alcohol in mouthwashes is added specifically to kill the bacteria that give you bad breath.
Actually, the concentration used is too low to kill microorganisms. Even Crest, which sells mouthwashes, admits as much on its website! It all has to do with concentration. Beers are 3-8% alcohol; wines are 7-18%; while spirits are 30% or greater. The disinfecting alcohol you buy at the drugstore is 70-99% alcohol. By comparison, mouthwashes have concentrations of alcohol up to 25%, which fall short of an antiseptic effect.
Not only that, but alcohol can actually make bad breath worse! That’s because it dries your mouth, which may actually provide a cozier environment for the bacteria that foul your breath
Alcohol in mouthwash is used as a carrier agent for ingredients like menthol as well as a preservative, not to kill bacteria. Using mouthwash will mask bad odour but will not get rid of the bacteria producing it.
If you want a mouthwash that is effective at reducing your risk of cavities (now known as “caries”) and gingivitis (gum inflammation), you may want to look at a “therapeutic mouthwash” to complement your dental hygiene routine. These mouthwashes contain an active ingredient like cetylpyridinium chloride, menthol or fluoride.