What are the causes of bad breath. i don't have bad breath, but what causes it?

Many causes: Plaque, germs, and food living on and in between teeth and under the gums. An unclean tongue. Gum disease. Cavities. Ill-fitting or loose dental crowns/bridges. A dental infection. There are many potential causes for bad breath.

Bacteria: Primarily bacteria. There are foods that can temporarily give you "bad breath". The oral cavity "mouth" is aerobic. When people have periodontal disease, there is a proliferation of anaerobic bacteria that should not be there. Some are really nasty and as they destroy the tissue and bone the smell is a necrotic dead smell. Other causes are the tongue and post nasal drip. See your dentist.

Etiology could: Be dental or medical dental from poor oral hygiene, periodontal disease tooth decay / infections; diet - coffee / tobacco .... Medical can stem from sinus issues , GI issues and the list goes on. Hope this helps.

Non-dental causes.: Aside from the usual dental culprits such as poor oral hygiene, infection, & periodontal disease...you can also get bad breath from acid reflux or a post-nasal drip. If your friend has good oral hygiene & no dental issues, then consider visiting your primary care physician or internist & getting checked out for any of the above health issues. Also, don' forget to cut back on the onions & garlic.

Bad breath: In the majority of cases, the cause of bad breath, or halitosis, is the product of bacteria in the mouth and gum disease. The proper diagnosis is the key to a successful treatment. See your dentist for Halimeter test, diagnosis and bad breath treatment that depends on its cause. Good luck.