Cure for Chapped Hands?

My mom's hands are always "raw" and "chapped." They are especially red around the knuckles. This "rawness" causes a burning of the hands. She has tried almost every product imaginable: Cetaphil, Cera Ve, Aquaphor, Vaseline, Aveeno lotion, Jergens lotion, Olive oil, Baby oil, Johnson & Johnson, etc. In addition, anything with fragrance will make her hands burn even more. Her dermatologist has gone as far as prescribing Tetrix, but that didn't work either. Does anyone have any idea on how to cure her "chapped hands?"