My armpits darkened in the past two years slowly. Although they are not very dark, but I am still conscious. I found out that the antiperspirant roll on I was using has expired long time ago. My bad, that must be the reason. I have stopped using it. But how do I make my armpits back to their original colour? Also, would a new roll on harm? Antiperspirant roll ons and deodorants are harmful or not?