A protective envelope for a lid of a plastic cup comprises a vacuous plastic film stuck on the top of the lid which was beforehand vaporized by an antiseptic liquid, without alcohol, then dried. The plastic film includes a detachable part, activated by a thread to be pulled, which is positioned above the opening to drink of the lid. So, when a consumer is ready to drink, he removes the detachable part by pulling the thread, so freeing the opening to drink. With such protection the lid is protected from bacteria and virus which can cause diseases. In brief, the steps of conception of the antiseptic lid are: to vaporize the lid with an antiseptic liquid without alcohol, to dry the lid, to put a thin film of plastic onto the lid by positioning the detachable part over the drink opening and to stick the film onto the lid by means of a vacuum.