A device, a system and a method are provided to accurately apply a medically beneficial substance directly to a laterally or superiorly located paranasal sinus cavity. When the device is assembled with a solution in a reservoir, and inverted such that the reservoir is above an input apparatus and a housing, weight of the solution pushes down on a diaphragm creating a negative pressure on the diaphragm, which prevents air from entering the reservoir and prevents a liquid from flowing out of the reservoir. Applying a positive pressure to a bottom of the diaphragm causes the diaphragm to open and allows air to flow into the reservoir. When a user creates the positive pressure by exhaling air into the device the act of exhaling causes the user's choana to close. Thereby any solution introduced into the user's sino-nasal cavity will remain contained within the user's sino-nasal cavity increasing effectiveness of treatment and decreasing user discomfort including gagging, choking, and inner ear disturbance. When the positive pressure on the bottom of the diaphragm is removed, the flow of the liquid from the reservoir stops.
