The invention relates to a hygienic device for constricting vessels (tourniquet) with a constricting belt which is connected to a closed circular belt by means of a lock. The tourniquet according to the invention is used in medicine. The aim of the invention is to design the lock of a tourniquet in such a way that, overall, a simpler disinfection possibility, such as a spray and wipe disinfection on site, can be carried out in order to prevent germ transport. In addition, it is the aim of the invention that the lock elements automatically find their locking position even in the event of inaccurate joining. The joining and release of the lock shall be carried out with one hand. According to the invention, a device for constricting vessels comprises a constricting belt and a lock, wherein a first end of the constricting belt is arranged in a fixed manner in the lock and a second end of the constricting belt is movably arranged in the lock. The constricting belt and the lock consist of a material having a smooth surface. In the closed state, the lock is a smooth, cube-shaped or elongated body which, apart from the supply means for the constricting belt, comprises no further external openings or projections.