A nasal cavity filter (2) having a substantially cylindrical supporting wall (4), which adheres to the walls of a nasal cavity, and an inner surface (5) of which defines a cavity (6) for the passage of air inhaled and exhaled by the user. The cavity (6) houses a number of fins (7), which generate turbulence in the air flowing through, and the surface of which impacted by the air retains particles present in the air.