May causes bad breath.

Unlike what most people think, the main cause of bad breath is bacteria. Halitosis is caused by certain bacteria healthy people who are in the soft tissues of the mouth and gums but especially in the rear surface of the tongue. These bacteria live under a "blanket" Mucous producing sulfur gases that cause unpleasant odors mouth.
It is possible to scientifically and objectively measure the odors that result from the oral cavity, including through appropriate measuring devices to record the concentration of sulfur molecules. Technically, the line between a fresh breath or bad is more or less 75 ppb (parts per trillion).
So the people that produce an unpleasant odor throughout the day (a phenomenon that clearly perceives its environment) are suffering from "halitosis" or "chronic halitosis". Scientific studies have shown that about 30% of the population complains of halitosis.