The invention relates to a microorganism reducing device, comprising a radiation device which is provided with a light source, a photosensitive substance which treats the area to be treated and is irradiated by said light source. The aim of said invention is to configure said device in such a way that it is possible to carry out an efficient and controllable treatment by means of operationally low-cost and easily handling apparatus. For this purpose, the inventive device comprises at least one applicator provided with a fibre-optic waveguide. In addition, the applicator and radiation device respectively comprise corresponding connector bodies coupling the applicator and radiation device in such a way that the light from the light source is emitted towards the treated area by means of the fibre-optic waveguide.
