Have you had this issue with a previous laptop?
Everyone's body chemistry is different, and also what you come into contact with on a daily business with your hands and palms.
Cleaning chemicals or suntan lotions and even skin lotions on your body and such can adversely react to the metals in the new UMBPs. Which in turn, could cause discoloration and wear.
For the palm areas(I hate to use them as, or call them, rests...) I use the Invisible Shield system. Works like a charm on the body also.