Bad breath can be caused by, and visible in, the cold
During winter, it may not be easy to smell when you have bad breath, even though you can often see it steaming in front of you. A recent article in Slate lamented that the computer-generated steam coming out of the actors’ mouths in the film The Social Network was visually unbelievable. Its accuracy notwithstanding, the film highlighted a common cause of bad breath - cold weather.
Repeatedly inhaling cold air can dry out the tongue, teeth and gums. Without saliva to cleanse the palate, anaerobic microorganisms begin to multiply in your mouth, releasing smelly sulfur compounds as they digest dead cells and food particles. The molecules given off by these bacteria largely account for the odor of halitosis.
The wintertime also typically sees an increase in sinus infections and colds. More than 1 billion colds occur each year in the U.S., according to the National Institutes of Health. The nose increases mucus production as the immune system battles germs. Much of this extra nasal moisture can run down the back of the throat. This trickle, known as post-nasal drip, can emit a foul odor, as well as provide oral bacteria with additional dead cells to subsist on.
To alleviate bad breath caused by cold, dry winter air, those with halitosis may consider using specialty breath fresheners that moisten the mouth and neutralize odors.