There are many possible reasons for bad breath. For people who are otherwise healthy, the tongue can be a common source for bad breath. The top surface of the tongue is host to thousands of microorganisms, some of which may release foul odors. These little bugs feed on the dead cell layer on the surface of the tongue. Scraping your tongue is an effective remedy. I like the serrated tongue scrapers available at the drug store. If you scrape your tongue once a day, you will be amazed what comes off. I do not believe the toothbrush does much to clean the tongue. Try scraping your tongue after brushing it and you may notice the brush did not accomplish much, compared with the scraper.