PROBLEM TO BE SOLVED: To provide pre-treatment agents that are excellent in suppressing hair damage in a one-part formula, and to provide oxidative hair dyeing methods and decolorizing methods using the pretreatment agents.SOLUTION: The present invention relates to a pretreatment agent to be applied to the hair before the application of an oxidative hair dye or a decolorizing agent, which contains one or more selected from citric acid, levulinic acid, and maleic acid, and is acidic and one-drug type, and to an oxidative hair dyeing method and a decolorizing method which comprises a pretreatment step of applying the pretreatment agent before performing an oxidative hair dyeing treatment or a decolorizing treatment.SELECTED DRAWING: NoneCOPYRIGHT: (C)2020,JPO&INPIT【課題】１剤式で毛髪損傷の抑制に優れる前処理剤、並びにこの前処理剤を使用する酸化染毛方法及び脱色方法の提供。【解決手段】前処理剤は、酸化染毛剤又は脱色剤を塗布する前の毛髪に塗布するものであって、クエン酸、レブリン酸及びマレイン酸から選ばれた一種又は二種以上が配合され、酸性、且つ、１剤式のものであり、酸化染毛方法及び脱色方法は、酸化染毛処理又は脱色処理を行う前にその前処理剤を塗布する前処理工程を備える。【選択図】なし
