  The critical skin effect, an intriguing phenomenon in non-Hermitian systems,
displays sensitivity to system size and manifests distinct dynamical behaviors.
In this work, we propose a novel scheme to achieve the critical non-Hermitian
skin effect of exciton polaritons in an elongated microcavity system. We show
that by utilising longitudinal-transverse spin splitting and
spin-momentum-locked gain, a critical non-Hermitian skin effect can be achieved
in a continuous system without the need of an underlying lattice. We find that
a phase transition can be induced by changing the cavity detuning with respect
to the exciton energy. We identify a measurable order parameter associated with
this phase transition and demonstrate the corresponding critical behavior. Our
work offers a flexible approach to manipulate non-Hermitian phases of exciton
polaritons, thereby expanding the potential applications of polaritonic
devices.
