Abstract: Apparatus and methods for dispensing an additive product through a showerhead are disclosed. In a first aspect of the invention, a system is provided in which a triggering mechanism such as motion detectors sense movement and actuate a valve, which in turn admits an additive product such as soap, shampoo or conditioner into a tube that is in turn connected to the showerhead assembly, which preferably has an internal venturi section into which the additive flows. The additive is mixed and aerated with the water flow and dispensed for a predetermined period of time, and then the valve closes. The motion detectors can also be used to adjust the predetermined period of time the material is dispensed. An improved venturi assembly is also disclosed.