My wife has some kind of rashes on the back of the palm. Any simple remedies?

Depends. You need to give a better description of the rash. Does it itch? Is it flat or raised? If they are linear and raised, it may be from a condition called lichen planus but without more details, any answer would be a guess at best.
Dr. can look at rash. Rashes are hard to describe in words. Usually, a doctor has to look at a rash to see what it might be. Very unusual rashes might need a skin biopsy. For common rashes such as eczema, mild reactions to plants or chemicals, excessive dryness, or little itchy bumps, over-the-counter Hydrocortisone 1% cream two or three times a day, for 1 week, usually helps until the rash can be examined by a doctor.