A one piece or two piece ostomy appliance comprising a base plate (1) the base plate comprising an adhesive wafer (11) that comprises a top film (8) and at least one skin friendly adhesive (9) on a proximal surface thereof for attaching the base plate to the skin of a user and a first through going hole (5). Further a convex element (10) is arranged distal to a user interface of the adhesive wafer and has a second through going hole (15) of the same diameter as the first through going hole and being co axially arranged therewith. The convex element comprises a material which reacts to moisture.
