PROBLEM TO BE SOLVED: To provide a device for prophylactic treatment of rhinitis, the device that can suppress the generation of substances causing a symptom such as hay fever or allergic rhinitis, and furthermore can be used preventively in common families.SOLUTION: A device has an insertion part 12 inserted in a nostril, and includes light supply means 10 provided with a light irradiation part 13 for applying the ultraviolet ray emitted from a light source to the outside in the insertion part 12. The light irradiation part 13 applies the ultraviolet ray with a central wavelength adjusted to 310 nm ± 2 nm to the outside. If the insertion part 12 is inserted in the nostril, the ultraviolet ray with the central wavelength adjusted to 310 nm ± 2 nm can be applied from the light irradiation part 13 in the nostril. Then, the applied ultraviolet wavelength is in the above range, so that the symptom of allergic rhinitis such as hay fever can be suppressed even if the strength of the ultraviolet ray is weak.
