Some causes of halitosis occur so regularly in our lives that we hardly give them a second thought. Dry mouth, pungent food, poor dental hygiene and morning breath are just a few of the things that can give you bad breath on a daily basis. Rarer causes of oral odor included illnesses, like the common cold.
The connection between nasal colds and bad breath has been established for a long time. Consider an 1889 issue of The Clinical Reporter, a homeopathic medicine and surgery journal, that discussed catarrh, which is an outdated name for the thick mucus we associate with the common cold.
The report stated that individuals suffering from inflamed mucus membranes would do well to apply a solution of sea salt and peroxide to the affected areas. The salt will clear up the catarrh, the author wrote, while "the spray of peroxide will remove all odor and bad breath in most cases."
While most physicians do not recommend this remedy for colds today, there is a physical principle behind the use of peroxide - it kills bacteria.
Like specialty breath freshening rinses and probiotics kits, peroxide would remove many odor-causing bacteria from the mouth and nasal passages. Instead of using sea salt however, it may better to brush regularly and keep the mouth moist.