Most of the black nasal discharge is caused by inhaling more black dust due to the harsh environment around, which is not a disease. However, long-term dust irritation can easily cause other nasal diseases, so we should not take it lightly. If the nasal discharge is clear, it may be an upper respiratory tract infection or allergic rhinitis attack. If it is yellow watery nasal mucus, it is mostly due to rupture of plasma cyst in maxillary sinus, mucopurulent nasal mucus is mostly seen in the late stage of cold, and yellow pus nasal mucus is mostly caused by bacterial infection. Bloody nasal discharge is mostly due to nasal trauma, inflammation and blood diseases will appear, and different treatment methods should be chosen according to different types of nasal discharge.