A trigger dispensing head applicable to a bottle of a trigger dispensing device for dispensing a product, comprising: - a frame, suitable for supporting the components of the head, comprising a main opening suitable to be in communication with an internal compartment of the bottle; - a cylinder chamber annularly delimited by a cylinder wall, having an inner chamber surface, and by a bottom wall at the bottom; - a manually-operable piston for translating between an initial rest position and a final end-of-stroke position; - a pressure chamber in which said piston operates; - a suction duct suitable for putting the internal compartment of the bottle in communication with the pressure chamber; - a dispensing duct suitable for putting the pressure chamber in communication with the external environment; - valve means for adjusting the product flow 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; - a sleeve having a sleeve axis, housed in the cylinder chamber, comprising: i) a bottom sleeve wall transverse to the sleeve axis; ii) an annular inner sleeve wall extending from said bottom sleeve wall and annularly delimiting the pressure chamber; iii) an annular outer sleeve wall extending from the bottom sleeve wall, positioned radially externally spaced from the inner sleeve wall and placed in contact with the inner chamber surface; wherein the dispensing head is characterized in that the sleeve also includes an annular vent wall that extends radially between the inner sleeve wall and the outer sleeve wall, internally delimiting a secondary vent passage passing radially in the inner sleeve wall and in the outer sleeve wall. - a frame, suitable for supporting the components of the head, comprising a main opening suitable to be in communication with an internal compartment of the bottle; - a cylinder chamber annularly delimited by a cylinder wall, having an inner chamber surface, and by a bottom wall at the bottom; - a manually-operable piston for translating between an initial rest position and a final end-of-stroke position; - a pressure chamber in which said piston operates; - a suction duct suitable for putting the internal compartment of the bottle in communication with the pressure chamber; - a dispensing duct suitable for putting the pressure chamber in communication with the external environment; - valve means for adjusting the product flow 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; - a sleeve having a sleeve axis, housed in the cylinder chamber, comprising: i) a bottom sleeve wall transverse to the sleeve axis; ii) an annular inner sleeve wall extending from said bottom sleeve wall and annularly delimiting the pressure chamber; iii) an annular outer sleeve wall extending from the bottom sleeve wall, positioned radially externally spaced from the inner sleeve wall and placed in contact with the inner chamber surface; i) a bottom sleeve wall transverse to the sleeve axis; ii) an annular inner sleeve wall extending from said bottom sleeve wall and annularly delimiting the pressure chamber; iii) an annular outer sleeve wall extending from the bottom sleeve wall, positioned radially externally spaced from the inner sleeve wall and placed in contact with the inner chamber surface;