Bad breath that you can’t smell by yourself may be due to the lack of sense of smell in the oral cavity, getting used to the taste of your own bad breath, and problems with your sense of smell. 1. No sense of smell in the mouth: the main reason why you can’t smell your own bad breath is that there is no sense of smell in the mouth, bad breath is mainly caused by poor oral hygiene, periodontitis, stone buildup and other aspects of the reasons that occur in the mouth. The olfactory nerve is mainly distributed in the nasal cavity. 2. accustomed to their own bad breath taste: bad breath can not smell their own may have been accustomed to the odor in the mouth, the oral cavity appeared to smell their own at the beginning of the odor, the beginning of the odor is very light, slowly and seriously, but the process of their own participation in the entire process has been subconsciously accustomed to the taste of halitosis, so do not feel that their own halitosis is what the problem is. 3. Problems with the sense of smell: If you cover your mouth and nose for haze, but can not smell their own bad breath, it is very likely that the sense of smell problems, the sense of smell is no longer sensitive, resulting in the inability to smell their own bad breath, which requires professional testing. Daily should pay attention to oral hygiene habits, maintain oral health, if there is a sense of smell problems should be timely medical treatment.