Dryer sheets

So far, we have not had mice in a camper. All entry points are sealed and periodically checked. Only the tires and tongue jack touch the ground. All food is removed, floors and counters cleaned after every trip. Also throw a couple of TomCat blocks in the underbelly twice a year.
I've also heard that Irish Spring soap works. We use it, so that might be a factor.
Now, ants, is a whole nother thing. Always have a supply of Terro baits spread out.