Many of the aforementioned works in polariton photochemistry have assumed that the optical cavity of study has a perfect internal reflectance with no loss of electro-magnetic energy to the outside world. In reality, the photonic modes inside every optical cavity have some non-zero coupling with the photonic modes outside the cavity, which causes cavity loss to occur. This cavity loss reduces excitation energy in the molecule-cavity system and can have significant effects on the outcomes of polariton-mediated reactions. Thus it is important to highlight the effects that cavity loss can have on simulations of polaritonic systems.