For the protection of an in-the-ear hearing aid against contamination by ear wax through the acoustic outlet port (34a) or a vent, a replaceable ear wax guard (36) is inserted in the aid and comprises an essentially tubular element with a through-going cavity and an abutment collar in one end for sealing abutment against the hearing aid housing (31). For an easy and safe insertion and removal of the ear wax guard (36), an applicator is used, which in one end has a smooth pin for introduction in the through-going cavity of the ear wax guard (36) and in the other end a harpoon-shaped catch member. For mounting of the ear wax guard (36) a hose or tube member serving as acoustic outlet canal (34) is connected to an abutment collar (33) in abutment with the outside of the hearing aid. The abutment collar is designed with oversize standard dimensions and adapted to an individually user-adapted hearing aid housing by preparation of its periphery edge.