A trigger dispensing head applicable to a bottle of a trigger dispensing device for dispensing a product, comprising: - a cylinder chamber annularly delimited by a cylinder wall, having an inner surface, and by a bottom wall at the bottom; - a piston which is manually operable to translate along an axial direction; - a pressure chamber onto which said piston operates; - a sleeve at least partially accommodated in the cylinder chamber, comprising an annular end wall defining a bottom opening of the sleeve, wherein the sleeve, the cylinder wall and the bottom wall define a valve compartment; - a suction duct adapted to put an inner compartment of the bottle in communication with the pressure chamber, comprising a suction mouth projecting axially from the bottom wall; - a dispensing duct adapted to put the pressure chamber in communication with the external environment; - valve means for adjusting the flow of product from the suction duct to the pressure chamber during a suction step and from the pressure chamber to the dispensing duct during a dispensing step, comprising a valve element in one piece, housed in said valve compartment, comprising: a) a tubular portion consisting of an annular valve wall extending along a valve axis, between a rear end defining a rear opening and a front end defining a front opening, said valve wall being fitted on the suction mouth; b) a flexible flap, connected in a cantilevered manner to the front end of the valve wall, radially projecting internally, provided, on the side facing the rear opening, with a shutter portion adapted to create a seal with the suction mouth for obtaining valve means; c) an annular membrane radially extending externally from the valve wall, adapted to abut against the annular end wall of the sleeve, thus creating a seal with the bottom opening for obtaining pre-compression valve means. - a cylinder chamber annularly delimited by a cylinder wall, having an inner surface, and by a bottom wall at the bottom; - a piston which is manually operable to translate along an axial direction; - a pressure chamber onto which said piston operates; - a sleeve at least partially accommodated in the cylinder chamber, comprising an annular end wall defining a bottom opening of the sleeve, wherein the sleeve, the cylinder wall and the bottom wall define a valve compartment; - a suction duct adapted to put an inner compartment of the bottle in communication with the pressure chamber, comprising a suction mouth projecting axially from the bottom wall; - a dispensing duct adapted to put the pressure chamber in communication with the external environment; - valve means for adjusting the flow of product from the suction duct to the pressure chamber during a suction step and from the pressure chamber to the dispensing duct during a dispensing step, comprising a valve element in one piece, housed in said valve compartment, comprising: a) a tubular portion consisting of an annular valve wall extending along a valve axis, between a rear end defining a rear opening and a front end defining a front opening, said valve wall being fitted on the suction mouth; b) a flexible flap, connected in a cantilevered manner to the front end of the valve wall, radially projecting internally, provided, on the side facing the rear opening, with a shutter portion adapted to create a seal with the suction mouth for obtaining valve means; c) an annular membrane radially extending externally from the valve wall, adapted to abut against the annular end wall of the sleeve, thus creating a seal with the bottom opening for obtaining pre-compression valve means. a) a tubular portion consisting of an annular valve wall extending along a valve axis, between a rear end defining a rear opening and a front end defining a front opening, said valve wall being fitted on the suction mouth; b) a flexible flap, connected in a cantilevered manner to the front end of the valve wall, radially projecting internally, provided, on the side facing the rear opening, with a shutter portion adapted to create a seal with the suction mouth for obtaining valve means; c) an annular membrane radially extending externally from the valve wall, adapted to abut against the annular end wall of the sleeve, thus creating a seal with the bottom opening for obtaining pre-compression valve means.