White spots, like the pigment has gone away? That's called vitiligo. It's fairly common. If you're going to be out in the sun, then put sunscreen on the affected area, as it's more prone to sunburn. These spots don't go away and there's not much you can do about them.
Causes? It could be genetic, chemical exposure, dietary/nutritional problems, auto-immune disease, thyroid issues, etc. It might be wise to see your dr and get a full blood panel done, just to rule out any other contributing factors.
Good luck and keep us posted!