A device for treating human skin by means of radiation, which device comprises a housing, a radiation source accommodated in the housing, a radiation exit opening, a radiation path between the radiation source and the radiation exit opening, and a radiation filter positioned in the radiation path and comprising water, characterized in that a radiation filter positioned in the radiation path and adapted to absorb radiation of a wavelength above a first threshold value and to substantially reflect or absorb radiation of a wavelength below a second threshold value.