A breath that is expelled which has unpleasant odor is called bad breath, and known as halitosis in medical terms. Bad breath odor can occur or strike anytime nor from time to time, it can also be long-lasting but it can always depend on what causes it. You may say that you have a clean mouth but do you know that there are actually millions of bad bacteria living inside your mouth, most particularly on the back of your tongue. Bacteria is the foremost reason of bad breath issues. When the mouth has low oxygen, it can be ideal for bad bacteria to grow and multiply fast. Most bad breath has mainly have something to do with the dirty and dry mouth.