Abstract: A device for limiting liquid loss in pressurized liquid dispensers having a membrane, which is elastically deformable and capable of occupying two positions, namely: (a) a resting position in which it has three support zones, namely on a first bearing surface and a second bearing surface and on the protruding part of head of knob; and (b) a deformed position in which its end of larger diameter is raised from the first bearing surface by the stress exerted by the pressurized liquid so as to leave a free passage for said liquid, membrane in this position, however, remaining in contact with the second bearing surface and with the protruding part of knob head.