You can tell if you have bad breath by testing yourself and by being told by others. Halitosis, which is the foul odor emanating from the mouth, nose, sinuses, pharynx, and esophagus, can affect people’s self-confidence and normal social interactions. The main methods to determine whether there is bad breath are: 1. their own test: to test their own bad breath, you can put your hand in front of the mouth closer to the place, do not completely cover the mouth, blowing to the palm of the hand, and then smell the smell of the palm of the hand, you can smell just exhaled the smell of the breath. 2. others told: you can let close people smell their own oral odor, to see if there is bad breath; or their own usually do not notice bad breath, often together with the people smell may inform their own.