Another thought...

You didn't say whether or not you stop working out during your visits. Besides increasing testosterone which can accelerate acne, the resulting sweat can block pores, increase bacteria and cause acne. You might try exfoliation in those areas to see if that helps.

If you're sure there is a difference between here and there, it should be easier to figure out than most people's Acne that doesn't give clues.

So, do you work out at the friend's or not?