I read over 2000 posts on chronic and persistent bad breath on another health forum going back 5 years. This is what I learned:
1. Acid Reflux causes irritation up to the nasal cavity and sinuses. It also upsets the acid balance in the mouth and can change the makeup of normal mouth bacteria and reduce the work of good scavenger bacteria. Acid reflux can be subtle (silent reflux) and not show up on tests, but it is now considered to be the number one cause of post nasal drip and chronic rhinitis, ahead of allergies. It is often mistaken for allergies.
2. Irritated sinuses lead to post nasal drip and sinus infections which can be subtle and not show up on cat scans
3. Post nasal drip mucous gives anerobic bacteria a place to breed on the tongue, particularly the back of the tongue that is in contact with the nasal mucous. Anerobic bacteria normally live in the gut and cause the smell we associate with feces. This is why often bad breath can "broadcast" across a room when you talk.
4. Tonsil stones cause bad breath but not all tonsil removals cure bad breath. Tonsil stones are the result of tonsil infection creating cavities in the tonsils. Tonsil infections are caused by post nasal drip from infected sinuses. Tonsil removal should be followed up with removal of sinus infection.
5. Often, people cannot smell their own bad breath as it gets blocked from consciousness. The hand lick test is bogus- anyone's saliva will smell with this test. It's a good way to sell mouthwash. A good friend or family member will help gauge the effectiveness of treatments.
6. It can be difficult to restore normal mouth conditions for normal bacteria colonization even after the cause of the mouth imbalance (usually acid-alkaline Ph) is cured.
7. Odor coming from the stomach or intestines is very rare.
8. Candida yeast fungus infection is a rare cause of chronic and persistent bad breath. Candida causes coated tongue and mouth surfaces and can be scraped. Chronic and persistent bad breath invariably includes a coated tongue. This, non-candida, coated tongue will not scrape or brush off and is the result of anerobic bacteria fastened to the cell walls of the tongue. Geographic tongue is a breeding ground for anerobic bacteria.
9. Most bad breath is not chronic and persistent and will respond to topical breath care products, herbal remedies, diet changes, etc.
10. Chronic and persistent bad breath is a handicap like any other, and can change your life for the worse. It requires strength of character to endure, patience and hard work to overcome, and an ability to cope with rejection and embarrassment and isolation. It is emphatically NOT the end of the world, however, and you can use the non-social time to improve your mind, learn about the world, explore interests and discover that you are much, much more than what is reflected off people.