Smell their nose stinks may be caused by fungal sinusitis, may also be odontogenic maxillary sinusitis, nasal foreign body secondary infection caused by. 1. Fungal sinusitis: Fungal sinusitis often occurs in the maxillary sinus, sieve sinus or pterygoid sinus on one side of the nasal cavity. The fungus colonizes the nasal cavity, causing nasal congestion, runny nose, headache, and causing a caseous fungal mass or odor to appear in the nasal cavity. 2. Odontogenic maxillary sinusitis: anaerobic infection of the maxillary sinus due to apical inflammation of the upper teeth leads to odontogenic maxillary sinusitis, with foul-smelling secretion, which is gray or green in color. 3. Nasal foreign body secondary infection: nasal foreign body exists for too long, there is decay and deterioration secondary infection, also can smell their nose stink. Smell their own nose smell there are other factors, such as purulent inflammation of the sinuses or sinus malignant tumors, etc., should be timely to the regular hospital otolaryngology outpatient clinic, systematic examination to clarify the diagnosis and etiology.