The main reasons for the involuntary yellow flow from the nostrils are acute upper respiratory tract infection, nasal inflammation, maxillary sinus cysts and so on. 1. Acute upper respiratory tract infection: acute attack of upper respiratory tract infection can cause runny nose, nasal congestion, cough and other phenomena, especially in the combination of bacterial infection can appear yellow purulent nasal mucus, so it will cause the nostrils unconsciously flow of yellow water. 2. Sinusitis: acute attack of sinusitis will lead to increased nasal secretion, secondary bacterial infection can appear yellow purulent secretion, can cause nostril involuntary yellow water phenomenon. 3. maxillary sinus cyst: maxillary sinus cyst belongs to the plasma cyst, after the rupture of the cyst can appear yellow water, so it will lead to the nostril involuntary flow of yellow water, mainly to the unilateral nostril flow of yellow water. There are many reasons for the involuntary flow of yellow water from the nostrils, after the symptoms need to go to the hospital in a timely manner to improve the examination, follow the doctor’s instructions to take standardized treatment, do not treat privately, so as not to lead to adverse consequences.