A dispensing system comprising: a container; a flowable base product contained within the container; a primary pump engine assembly mounted on the container and in fluid communication with the flowable base product; and a co-acting dispensing head mounted on and in fluid communication with the primary pump engine assembly, the co-acting dispensing head containing an active ingredient formulation to be mixed with the flowable base product, characterized in that the co-acting dispensing head further comprises: a nozzle body having a bottom wall with an inlet orifice and an outer side wall with a dispensing orifice; a cap attached to the nozzle body; a nozzle core co-axially received in the nozzle body and having an annular piston seat, a flow aperture through the annular piston seat, and a recessed flow channel extending from an upper lip to a bottom edge of an outer surface of the nozzle core; a base product flow channel between the nozzle body and the nozzle core connecting the inlet orifice with the recessed flow channel; and a cup-shaped piston seated on the annular piston seat configured such that an active ingredient chamber is defined above the cup-shaped piston, between the cup-shaped piston and the cap, the active ingredient formulation being contained in the active ingredient chamber, and the cup-shaped piston configured such that a lower base product chamber space is defined below said cup-shaped piston, between said cup-shaped piston and the nozzle core; wherein, the recessed flow channel is aligned with the dispensing orifice and defines a flow path for active ingredient formulation exiting from the active ingredient chamber and for flowable base product exiting the base product flow channel to mix before exiting the dispensing orifice. a container; a flowable base product contained within the container; a primary pump engine assembly mounted on the container and in fluid communication with the flowable base product; and a co-acting dispensing head mounted on and in fluid communication with the primary pump engine assembly, the co-acting dispensing head containing an active ingredient formulation to be mixed with the flowable base product, characterized in that the co-acting dispensing head further comprises: a nozzle body having a bottom wall with an inlet orifice and an outer side wall with a dispensing orifice; a cap attached to the nozzle body; a nozzle core co-axially received in the nozzle body and having an annular piston seat, a flow aperture through the annular piston seat, and a recessed flow channel extending from an upper lip to a bottom edge of an outer surface of the nozzle core; a base product flow channel between the nozzle body and the nozzle core connecting the inlet orifice with the recessed flow channel; and a cup-shaped piston seated on the annular piston seat configured such that an active ingredient chamber is defined above the cup-shaped piston, between the cup-shaped piston and the cap, the active ingredient formulation being contained in the active ingredient chamber, and the cup-shaped piston configured such that a lower base product chamber space is defined below said cup-shaped piston, between said cup-shaped piston and the nozzle core; a nozzle body having a bottom wall with an inlet orifice and an outer side wall with a dispensing orifice; a cap attached to the nozzle body; a nozzle core co-axially received in the nozzle body and having an annular piston seat, a flow aperture through the annular piston seat, and a recessed flow channel extending from an upper lip to a bottom edge of an outer surface of the nozzle core; a base product flow channel between the nozzle body and the nozzle core connecting the inlet orifice with the recessed flow channel; and a cup-shaped piston seated on the annular piston seat configured such that an active ingredient chamber is defined above the cup-shaped piston, between the cup-shaped piston and the cap, the active ingredient formulation being contained in the active ingredient chamber, and the cup-shaped piston configured such that a lower base product chamber space is defined below said cup-shaped piston, between said cup-shaped piston and the nozzle core; wherein, the recessed flow channel is aligned with the dispensing orifice and defines a flow path for active ingredient formulation exiting from the active ingredient chamber and for flowable base product exiting the base product flow channel to mix before exiting the dispensing orifice.