Abstract: An apparatus for treating (e.g. dyeing) hair, utilizing a treatment liquid which is a mixture of several components, has a cylindrical container with an open end to which an attachment with a hollow comb structure for the discharge of the liquid mixture is threadedly secured. The discharge is effected by the release of a spring-loaded piston inside the container from a retracted position. To mix the several components, a perforated disc may be axially reciprocated in the container between the piston head and the attachment; the disc may have a stem passing through the hollow piston rod to the outside and terminating in a manipulating knob which in one embodiment may be rotated relatively to the piston into a position wherein the perforations of the disc are aligned with similar perforations of the piston head so that mixing is accomplished by joint reciprocation of that head and the disc.