A bit of yellow snot may be caused by acute rhinitis, nasal polyps, sinusitis and other factors. 1. Acute rhinitis secondary bacterial infection: may be related to viral infection, infection of the nasal mucosa and submucosal tissues, in the early stage is usually white mucus-like nasal mucus, secondary bacterial infection, there will be yellow nasal mucus, may also be accompanied by nasal itching, sneezing, nasal congestion and other symptoms. 2. Nasal polyps: a common benign growth in the nasal cavity, may be caused by chronic inflammatory stimulation, when combined with bacterial infection, it will lead to yellow nasal discharge, may also be accompanied by nasal congestion, sneezing, nasal breathing difficulties and other symptoms. 3. Sinusitis: it may be related to respiratory tract infections, respiratory allergic reactions, and poor dietary habits, which may cause the presence of purulent substances in the nasal mucus, resulting in yellow nasal discharge, which may be accompanied by symptoms such as dizziness, headache, and olfactory disorders. A bit of yellow nasal discharge, and accompanied by other abnormal manifestations, should be vigilant for disease factors, should also seek medical treatment to avoid aggravation of the disease.