My sister used to say all the time last year that she could smell her own breath and it would smell like BM. We would laugh so hard because we could not smell it. However, she pursued this by going to the dentist, eyes-nose-throat doctor, her own internist, and finally went to a gastroenterologist. She had a scope to the sinuses and even an MRI because one doctor said her smelling that bad smell could be a brain tumor. The gastorenterologist (stomach doctor) gave her a very simple test. She had to drink some kind of sugary fluid and breathe into a test jar. And the cause was found. It was actually, as someone said, coming from her bowel and did smell bad. It was methane gas. She was supposed to be on an antibiotic, but could not take it right away, so instead took yogurt with extra acidophilus and then took the acidophilus pills. She no longer has the issue. Several people I have told this story to have had the same results with the test and have taken the antibiotic with a resulting "cure" and no further problems. Worth looking into. Good luck.