Most cases of bad smell after wearing a mask for a long time is that the patient’s own mouth has a bad smell, which is a very common clinical situation. Because the oral cavity itself is a complex and bacterial environment, the teeth in the oral cavity often have cavities, pulpitis, apical infection and other diseases, and the mucous membrane in the oral cavity also has various diseases such as mouth ulcers. These diseases may cause some disease-causing bacteria to colonize in the mouth, and some of these bacteria will produce certain gases, which will produce bad odor. And after wearing the mask, these gases will be adsorbed to the mask with breathing, so when you wear the mask, you will feel the obvious odor.