What is the ruling regarding the purity of this fluid that exits the nose—which resembles cerebrospinal fluid?

What exits a human being is divided into three categories:

1. Pure without dispute, such as: tears, sweat, saliva, nasal discharge, and spit.

2. Impure without dispute, such as: urine, prostatic fluid (wady), blood, and similar substances.

3. Disputed, such as: semen and stomach phlegm.