Provided is a therapeutic agent capable of treating allergic rhinitis in a safe, simple, and noninvasive manner substantially without side effects and physical distress to patients. Provided is a therapeutic agent for allergic rhinitis for 5-aminolevulinic acid-based photodynamic therapy (ALA-PDT) comprising 5-aminolevulinic acid (ALA) or a derivative thereof, or a salt of the 5-aminolevulinic acid or the derivative as an active ingredient, and used in ALA-PDT in which light having a wavelength of 400 nm to 700 nm is irradiated; and particularly provided is a therapeutic agent for allergic rhinitis in a locally applied solution form, a water-soluble ointment-dissolved form, a jelly-dissolved form, or the like. The therapeutic agent does not require the conduct of 5-aminolevulinic acid-based photodynamic diagnosis (ALA-PDD) for detecting a site of protoporphyrin IX (PpIX) accumulation radiating light having a wavelength of 610 nm to 650 nm under irradiation of excitation light having a wavelength of 380 nm to 420 nm before ALA-PDT.