A dispenser device without any air intake, such as an airless pump, for dispensing a fluid substance, the device comprising a dispensing chamber (14) of variable volume, which chamber is provided with an inlet (12) equipped with an inlet valve member (51, 53), and is provided with an outlet equipped with an outlet valve member, the dispenser further comprising a piston (3) for causing the volume of the dispensing chamber (14) to vary, closure elements (51; 52; 55; 63) being provided to close off the dispensing chamber (14) in airtight manner, substantially at its inlet (12), prior to it being used for the first time, the device being characterized in that the closure elements are formed by the inlet valve member (51, 53).