Sneezing smells bad clinically for the following reasons: First, diseases related to the airways of the lungs, especially inflammatory infections and purulent infections, which can lead to the formation of odor by spraying saliva out when sneezing. Second, diseases of the gastrointestinal tract, such as indigestion and Helicobacter pylori infection, when sneezing will bring the odor through the gastrointestinal tract into the nasal cavity and thus spray out. Third, chronic pharyngitis, the retention of secretions in the throat can lead to odor. Fourth, gum disease, such as chronic gingivitis, gum calculus, halitosis and other related diseases, will also appear odor. Fifth, rhinitis, sinusitis, nasal malignancy, nasal foreign body, etc., when sneezing the odor in the nasal cavity can be sprayed out. All in all, if you sneeze and have a bad smell, it may not be a big problem once in a while, but if it occurs repeatedly, it is recommended to go to the hospital for consultation to find the cause for symptomatic treatment.