After a night’s sleep, abnormal odors may develop in the mouth. Brushing your teeth immediately after waking up, drinking some water and maintaining good habits can quickly clear your mouth of odor and help prevent bad breath in the morning. Brushing your teeth is the most important measure to maintain a normal taste in your mouth. The mouth is actually an important place for bacteria to colonize. Careful brushing after waking up in the morning can effectively remove some of the smelly chemicals produced by the metabolic process of these bacteria. Brushing must be done carefully, and the inner and outer sides of the upper and lower teeth rows and the tongue should be brushed. Toothbrushes should be replaced every 2-3 months, and they should be placed in a ventilated environment to reduce the growth of bacteria that can be carried into the mouth during the brushing process. After brushing your teeth, drink some plain water. Adequate water can make the mouth moist again and reduce the growth of bacteria in the mouth. As you swallow, many bacteria and chemicals that produce abnormal taste will be brought into the gastrointestinal tract by the flushing action of water and neutralized by the acidic environment of the gastrointestinal tract, which can further reduce the amount of substances that produce bad breath. Usually, do not drink too much coffee, alcohol and smoke before going to bed. These habits, may be some of the causes of bad breath in the morning. After drinking coffee, this drink may change overnight and produce bad breath smell in the morning. Alcohol can reduce the secretion of oral saliva at night, resulting in enhanced bacterial metabolism at night and abnormal odor. The smell of burning tobacco can itself produce bad breath after an overnight stay. These habits should be avoided for a short period of time away from sleep. Bad breath in the morning can be effectively improved and prevented by these measures. Of course, some oral diseases can also cause bad breath, which requires prompt treatment.