The invention relates to an applicator for a nasal cannula, comprising a body (11) enclosing a hollow space (22). The applicator further comprises tube connections (20, 21) for supplying a respirable gas into the hollow space (22). The applicator further comprises prongs (18, 19) for administering the respirable gas into the nostrils of a person. A valve (15, 16, 17, 38, 42) is located in a wall of the body (11) so that respirable gas can flow from the outside through the valve into the hollow space (22), but not in the reverse direction. The invention further relates to an applicator having a top of sealing cones (23, 24), wherein the sealing cones (23, 24) may be provided with rim-shaped sealing lips on their side facing away from the body (11), which produce a tight seal with the inner wall of the respective nostril.
