What Causes Dry Patches On The Stomach And Back?

good afternoon, I am a 31 year old female about 140lbs. I noticed a small patch of dry skin on my upper thigh about 2 months ago. It went away with cream but appeared again a week ago as a bruise (which isn't painful). I now notice I have the same dry patch on my stomach and back. The patches are only small but have a different texture to my normal skin. Any ideas?