An apparatus comprising: a fluid discharge orifice defined in a distal end of a nasal stopper, the distal end being sufficiently small in cross-section as to permit entrance of the discharge orifice into a nostril opening of a human child, a proximal portion of the nasal stopper comprising a shield configured to resist over-insertion of the discharge orifice into the opening; and a stem structured to provide a lumen for communication of treatment fluid to a turbine chamber for discharge of the fluid substantially as a mist from the discharge opening, the stem extending in a length direction between a proximal end and a distal end, the nasal stopper being affixed to the distal end of the stem; wherein a thread structure carried at the proximal end of the stem is configured to couple with a luer-locking portion of a syringe; and wherein the combination of the stem assembled to the nasal stopper is operable as an atomising nozzle, the atomising nozzle comprising the discharge orifice, the discharge orifice being disposed in a wetted fluid path to conduct fluid from the turbine chamber; wherein a first cooperating coupling structure (170, 172) is carried between the stem and the nasal stopper which is configured to form a distal fluid seal to resist leakage of fluid from the lumen; and wherein second cooperating coupling structure (176, 178) is carried between the stem and the nasal stopper is configured to form a primary torsion-carrying coupling; wherein the stem is configured to couple with the nasal stopper; and a portion of a proximal wall of the turbine chamber is defined by a structure disposed at a distal end of the stem to assist in discharge of the treatment fluid in misted, or atomised, form. a fluid discharge orifice defined in a distal end of a nasal stopper, the distal end being sufficiently small in cross-section as to permit entrance of the discharge orifice into a nostril opening of a human child, a proximal portion of the nasal stopper comprising a shield configured to resist over-insertion of the discharge orifice into the opening; and a stem structured to provide a lumen for communication of treatment fluid to a turbine chamber for discharge of the fluid substantially as a mist from the discharge opening, the stem extending in a length direction between a proximal end and a distal end, the nasal stopper being affixed to the distal end of the stem; wherein a thread structure carried at the proximal end of the stem is configured to couple with a luer-locking portion of a syringe; and wherein the combination of the stem assembled to the nasal stopper is operable as an atomising nozzle, the atomising nozzle comprising the discharge orifice, the discharge orifice being disposed in a wetted fluid path to conduct fluid from the turbine chamber; wherein a first cooperating coupling structure (170, 172) is carried between the stem and the nasal stopper which is configured to form a distal fluid seal to resist leakage of fluid from the lumen; and wherein second cooperating coupling structure (176, 178) is carried between the stem and the nasal stopper is configured to form a primary torsion-carrying coupling; wherein the stem is configured to couple with the nasal stopper; and a portion of a proximal wall of the turbine chamber is defined by a structure disposed at a distal end of the stem to assist in discharge of the treatment fluid in misted, or atomised, form.