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 (M), housed in the cylinder chamber , comprising: i) a bottom sleeve wall transverse to the sleeve axis (M); 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 (M), housed in the cylinder chamber , comprising: i) a bottom sleeve wall transverse to the sleeve axis (M); 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 (M); 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 ; <EOS>