My sister had severe eczema as a teenager on her back, lower stomach and groin.
Light treatments were the only thing that cleared it up for her.
My DH has chronic psoriasis, light treatments worked for him also.
My other sister has an undiagnosed skin condition that nothing works for...... She has seen a skin specialist, and still no answers.

It's horrible not being able to find anything that works
My sister eventually grew out of her eczema in her mid-20's.
I hope you can find something that works for DD.
My DH hated wearing shorts and even stopped playing football as a teenager, because people would stare at him he was a leper.