I say, and with God's success: mucus, tears, saliva, and sweat, all do not invalidate [purity]; due to their lack of impurity. Refer to: Fath Bab al-Ianaya 1: 61, and the notes extracted on al-Naqaya p. 4, and al-Ikhtiyar li Ta'lil al-Mukhtar 1: 16, and God knows best.