A device for packaging and applying a substance constituting a cosmetic or a care product containing at least one volatile hydrocarbon solvent can be closed hermetically and comprising comprises at least two elements, at least one of which is made of a plastics material. Said elements are suitable for moving relative to each other in order to enable the substance to be applied. The plastics material is selected in such a manner that the element(s) is/are not subject to significant mass variation when put into prolonged contact with the vapor of said solvent.