An illumination device (10; 110) of at least one lock of keratinic fibers, including: - a first branch defining a first confinement surface; - a second branch, defining a second confinement surface intended to be placed across from the first confinement surface, the first branch and the second branch being movable relative to one another between an open position for insertion of the lock and a closed position for illumination of the lock in which the confinement surfaces (44, 64) define a cavity for illumination of the lock, the illumination cavity opening onto a first side edge of the illumination cavity by a first side slit for accessing the illumination cavity and onto a second opposite side edge of the illumination cavity, by a second side slit for accessing the illumination cavity; - an assembly for illumination of the lock in the illumination cavity, able to illuminate the lock with a light having a wavelength between 200 nm and 700 nm, in particular between 280 nm and 700 nm, - a first confinement member on the first side edge of the illumination cavity and coming from the first confinement surface, the second confinement surface, or their peripheries, - a second confinement member, on the second side edge of the illumination cavity and coming from the first confinement surface, the second confinement surface, or their peripheries, characterized by the first confinement member extending in the first lateral slit over substantially the entire length of the first side slit, the second confinement member extending in the second lateral slit over substantially the entire length of the second side slit, each confinement member (80, 82) optically closing the illumination cavity over its entire length when the device is in the closed position, wherein the first confinement member and/or the second confinement member is formed by a curtain of bristles and/or wherein the device comprises a first additional confinement member positioned opposite the first confinement member in the closed position; or wherein at least one of the confinement members (80, 82) being formed by a sheet of flexible material opaque to the UV/Visible rays. - a first branch defining a first confinement surface; - a second branch, defining a second confinement surface intended to be placed across from the first confinement surface, the first branch and the second branch being movable relative to one another between an open position for insertion of the lock and a closed position for illumination of the lock in which the confinement surfaces (44, 64) define a cavity for illumination of the lock, the illumination cavity opening onto a first side edge of the illumination cavity by a first side slit for accessing the illumination cavity and onto a second opposite side edge of the illumination cavity, by a second side slit for accessing the illumination cavity; - an assembly for illumination of the lock in the illumination cavity, able to illuminate the lock with a light having a wavelength between 200 nm and 700 nm, in particular between 280 nm and 700 nm, - a first confinement member on the first side edge of the illumination cavity and coming from the first confinement surface, the second confinement surface, or their peripheries, - a second confinement member, on the second side edge of the illumination cavity and coming from the first confinement surface, the second confinement surface, or their peripheries, characterized by the first confinement member extending in the first lateral slit over substantially the entire length of the first side slit, the second confinement member extending in the second lateral slit over substantially the entire length of the second side slit, each confinement member (80, 82) optically closing the illumination cavity over its entire length when the device is in the closed position, wherein the first confinement member and/or the second confinement member is formed by a curtain of bristles and/or wherein the device comprises a first additional confinement member positioned opposite the first confinement member in the closed position; or wherein at least one of the confinement members (80, 82) being formed by a sheet of flexible material opaque to the UV/Visible rays.