The invention relates to a dispensing head comprising an insert (20) provided with a cam surface, a ring (10) on which is articulated a lever (30) provided with a trigger, and at least one cam follower. The lever and the cam surface can rotate relative to each other between a closed position and an open position. According to the invention, the insert (20) is configured to be blocked in rotation relative to the container (80) and to the stem (81) of the valve, the ring is an adjustment ring (10) which is configured to rotate relative to the container (80) and to the insert (20) about the main axis (A) of the valve to bring the lever (30) and the cam surface (22) into an open or closed position. Tamper-evident means can be provided in the insert to ensure the integrity of the dispensing head before the first use.