I get rashes on the top of my thighs from shorts with grippers too. I have a couple pairs of shorts that have no grippers (so much more comfortable!) but they have thin pads. It's always a toss up whether I want thigh comfort or butt comfort lol.

I haven't figured out the rash yet either but I have found it gets a little scabby/dried out and goes away after I've been in the pool.