Reducing agent injection nozzle

An injection nozzle (1) for injection of a reducing agent into an exhaust gas system (2) of an internal combustion engine for selective catalytic reduction, for atomization by means of compressed air or propellant gas, the nozzle (1) having at least one outlet opening, wherein the nozzle (1) upstream of the outlet opening has a variable volume (8) which after completion of injection of the liquid is increased in order to draw gas from the vicinity (2) through the outlet opening into the nozzle (1), wherein the variable volume (8) is delimited by a position-variable, flexible element (6), which can be deflected out of its rest position in order to reduce the variable volume (8), and which has reset forces to automatically return to its rest position in order to increase the variable volume (8), and wherein the variable volume (8) is delimited by a flexible element (6) which during injection of the liquid is deflected out of its rest position in order to reduce the variable volume (8), after completion of the injection of the liquid the flexible element (6) returning to its rest position and increasing the variable volume (8).