I was asking because, for example, with my STIM electrode gel pads, they come with individually wrapped "cleansing cloths" to wipe/cleanse the skin before application to help the pad adhere.
I sometimes will use soap and warm water on a face cloth and make sure I really cleanse the area well. Not scrub it raw or exfoliate your tender skin, but make sure you remove dead skin cells, leftover adhesive, and sweat.
Just a simple rinse won't usually get all of that off.
If there's anything between the surface of the gel adhesive and the surface of your skin, it can act as a barrier and interrupt the flow of medicine or even peel off or lift at the edges or slide around because it can't really stick.
I don't know if this is do-able with your patches, it's just a thought.