While the notion of open quantum systems is itself old, many of the existing studies deal with quantum mechanical systems rather than quantum field theories. In this talk, I will begin with a brief review of field theoretical/path integral tools currently available to deal with open quantum field theories. Then, I will go on to apply these tools to an open version of $\phi^4$ theory in four spacetime dimensions and its one loop renormalisability. I will also comment on the renormalisability of Lindblad structure.
