Administration of medicine or medicated oil through nose is known as Nasya Karma.
Nasa is said to be the door of the Shiras. Medicine administered through the nose, spreads through the Shiras and helps in the evacuation of Dosha, thereby pacifying the diseases.
Nasya Karma is the main line of treatment for diseases above the clavicle and it is the only Shodhana Karma for Urdhwanga.