Dispenser head attachable to a container of a trigger dispenser device, comprising: a) a pressure chamber and a piston operable by the trigger and sliding in a main compartment of said pressure chamber along a pressure axis, operating in pressure in said main compartment during an active step and operating in negative pressure in said main compartment during a return step; b) a dispenser duct suitable for being placed in communication with the main compartment of the pressure chamber, for dispensing the liquid towards the outside; c) valve dispenser means, operating between said main compartment and said dispenser duct and normally closed, suitable, in an open configuration during said active step, to permit the passage of the liquid from the main compartment towards the dispenser duct upon exceeding a threshold pressure; d) trigger means suitable for mechanically operating on said dispenser valve means to force them towards the open configuration, characterised in that the trigger means comprise the piston being suitable to interfere mechanically with the valve dispenser means; characterised in that - the valve dispenser means comprise a flexible membrane and an abutment wall of a sleeve rigid in relation to the membrane, which defines an opening suitable for placing the main compartment in communication with the dispenser duct, wherein the membrane, in a rest configuration, closes said opening; - the dispenser head comprises check valve means suitable for preventing the return of the liquid from the main compartment to the inner compartment of the container during the active step, and said check valve means comprises a tang projecting axially from the membrane and a lip partially separated from the tang by means of a cut; - the piston has a main side with a recess, so that the lip is housed in the recess of the piston when the piston forces the valve dispenser means. a) a pressure chamber and a piston operable by the trigger and sliding in a main compartment of said pressure chamber along a pressure axis, operating in pressure in said main compartment during an active step and operating in negative pressure in said main compartment during a return step; b) a dispenser duct suitable for being placed in communication with the main compartment of the pressure chamber, for dispensing the liquid towards the outside; c) valve dispenser means, operating between said main compartment and said dispenser duct and normally closed, suitable, in an open configuration during said active step, to permit the passage of the liquid from the main compartment towards the dispenser duct upon exceeding a threshold pressure; d) trigger means suitable for mechanically operating on said dispenser valve means to force them towards the open configuration, characterised in that the trigger means comprise the piston being suitable to interfere mechanically with the valve dispenser means; characterised in that - the valve dispenser means comprise a flexible membrane and an abutment wall of a sleeve rigid in relation to the membrane, which defines an opening suitable for placing the main compartment in communication with the dispenser duct, wherein the membrane, in a rest configuration, closes said opening; - the dispenser head comprises check valve means suitable for preventing the return of the liquid from the main compartment to the inner compartment of the container during the active step, and said check valve means comprises a tang projecting axially from the membrane and a lip partially separated from the tang by means of a cut; - the piston has a main side with a recess, so that the lip is housed in the recess of the piston when the piston forces the valve dispenser means. - the valve dispenser means comprise a flexible membrane and an abutment wall of a sleeve rigid in relation to the membrane, which defines an opening suitable for placing the main compartment in communication with the dispenser duct, wherein the membrane, in a rest configuration, closes said opening; - the dispenser head comprises check valve means suitable for preventing the return of the liquid from the main compartment to the inner compartment of the container during the active step, and said check valve means comprises a tang projecting axially from the membrane and a lip partially separated from the tang by means of a cut; - the piston has a main side with a recess, so that the lip is housed in the recess of the piston when the piston forces the valve dispenser means.