My sister always has dry, flaky, itchy hands because she's a hygiene freak. She constantly washes her hands and uses hand sanitizer which has caused her skin to be extremely dry and itchy. Her doctor has diagnosed her with dermatitis. She is using a special cream on her hands now and she is not allowed to wash her hands more than necessary.
She's also starting therapy because apparently, too much stress and worrying can lead to this kind of obsession about hygiene.