The first thing to consider is cerebrospinal fluid rhinorrhea. The first thing to consider is cerebrospinal fluid rhinorrhea, which is usually caused by trauma or previous surgery in the nasal cavity, and cerebrospinal fluid rhinorrhea is usually a colorless liquid that does not crust after drying. Next is to consider allergic rhinitis, for allergic rhinitis in addition to the nose flowing clear water, there may be symptoms such as sneezing, nasal itching, nasal congestion, etc., as long as timely anti-allergy treatment can control the symptoms. Then also to exclude whether the cysts of the maxillary sinus, for the maxillary sinus cysts outflow of clear water will usually become yellowish, if you want to confirm the diagnosis, just do sinus CT can. So if you want to really clarify what the cause is, it is best to go to the ENT department of the hospital for further consultation.