I am 22 years old (female) and a couple years ago I started getting white spots on my arms, like there is a loss of pigmentation. These spots tan lighter than the rest of my arms. I thought it was just dry skin, but i have been putting good lotion on, often and it doesn't seem to help. What causes this skin change and is there anything i can do?

Optional Information:
Female , Age: 22

Already Tried:
Eucerin extra dry skin lotion and Dove body wash