One must first determine where the bad smell is originating.
Here are a few tests to try..
Have a trusted person give you some feedback...
1/ Breathe out through your mouth and see if that smells so bad to the person
2/ Close your mouth and breath out only through your nose.
3/ If there is no difference, the smell is originating in the lungs.
4/ If the smell is worse when breathing through your mouth, then one would think that it is coming from the mouth. Maybe NOT.
5/ Try to burp and have that person tell you if the smell is the same as the breath or not. If it is the same or worse then the esophagus or stomach might well be to blame.
6/ If it is different or less offensive, then the stomach and esophagus are
probably not the source.
7/ If the smelll is only bad when breathing through your nose, then you must rule out a sinus infection. A nasal swab would be a good thing to culture.
(Many people carry a Staph Aureus bacteria in their noses/sinuses and if Acne is also a problem on the face, this may be the cause as well.)
If you do not have a trusted person to smell your breath, then you can get some information from a pet dog especially if they revolt from both your mouth and nose breath.
If you have a spouse or mate, they may also have the same bad breath and not notice yours very much. You may also not be offended by theirs.
Ask yourself if you have had an improvement in breath when taking Antibiotics .
If so, then maybe you did not take them long enough to clear up a difficult infection. Your doctor may be willing to prescribe longer, but some are not so understanding.
If you are sexually active, you may have picked up a hard to diagnose infection from your partner... Bacteria such as Mycoplasma, Ureaplasma and Chlamydia will not culture on the usual petri dish media. If your doctor is a thinker, he will say... ""We can't find anything obvious to treat, but something
must be causing the offensive smell, so lets try a week of Zithromax which will
treat the hidden bacteria as well."" If it works, that must have been the problem. Of course, your mate may need to be treated at the same time or reinfection can easily occur .
If the smell is coming from the stomach, poor digestion, a weak or open sphincter, or a gastric infection with Helicobacter Pylori should be ruled out.
A blood test for Helicobacter Pylori or a breath test for Urea would be a big help. (The Urea smell may be the source of the bad breath.)
If that was positive, then a week of two Antibiotics and an ulcer med
like prilosec or omeprazole would be the first thing to try.. This is called the
"Triple Therapy" and has been accepted treatment for at least 8 years.
Symptoms may include, belching, burping and burning in the stomach which gets better after eating for an hour or so... a white coated tongue, bad breath, and a sour taste in the mouth. If you have this... Get tested.
If your doctor will not test for HP, then you need another doctor.
If the test is negative, (which is possible) taking the triple therapy may still
be helpful because not all Helicobacter strains are detectable.
If you have hurt your esophagus in a car accident where whiplash was involved, or have injured yourself in the mid chest area while doing too many
ab-crunches, it is possible that an important sphincter called the "Lower Esophageal Sphincer" and the "Phrenoesophageal Ligament"
were damaged leaving you with a problem called acid reflux (gerd) that could be allowing stomach acid to burn the delicate esophageal tissue and cause the smell of rotting meat that is offending others. Surgery may be needed if this is the case. Sinus problems that resemble an infection can be due to
breathing these acid fumes through delicate nasal membranes.
If you need more info on such problems, do a search on "heartburn" or any of the other words in brackets.