Abstract: A mixer and a method therein, including feeding a rotating flow of exhaust gas in a mixing pipe towards a turning end of a mixing chamber; dosing reactant by a doser against the rotating flow around a centreline of the mixing pipe; maintaining a guide around the doser such that a front face of the guide faces the rotating flow, and the guide defines a central opening surrounding the doser; guiding a side flow out of the rotating flow to a carrier flow around the doser via the central opening; and inhibiting by the guide turbulence from being transferred from the side flow to the carrier flow.