What Causes Dark Patches Above Chest And Hands?

Hi, I am a 28 yr old women, I have develpoed a dark patch above my chest which is a little itchy at times,I recently went for a hand wax and I noticed that I developed similar patches on 2 places in my hands, it's itchy too. I dont know if both are the same since what I saw ony my hands came only after waxing the other patch was there from quite some time.. can u help me??