The invention relates to an agent for cleaning interdental toothbrushes, said agent consisting of a first and a second kneadable and mouldable mass, the masses being used separately. Both masses have the same base composition. The composition comprises hydroxy propylated polygalactomannan and between 75 % by weight and 97 % by weight of bonded water and a liquid antiseptic solvent component, the first kneadable and mouldable mass containing predominantly sterilising active ingredients, whereas the second kneadable and mouldable mass contains disinfecting, antiseptic active ingredients for dental hygiene. The first kneadable and mouldable mass is designed to clean the interdental brush and collects solid particles that adhere to the brush. Said mass is also designed to sterilise the interdental brush, while the second kneadable and mouldable mass predominantly contains antiseptic agents which are applied to the brush before the latter is used or re-used. The invention also relates to a device for using the interdental brush cleaning agent. Said device consists of two separate containers that are held together and separately contain the first and second kneadable and mouldable mass. Each container preferably has a number of chambers and its own sealing cap, the lower part of which is provided with insertion openings (10), each of which communicates with one chamber (9). Both containers (2, 2') are held together with their bases facing each other by means of a clip-type retaining device (4).