What causes light blotches in my tan?!

What causes light blotches in my tan?

I've been working for the parks department this summer so am outside ALL the TIME and am pretty tan as a result. One day, I noticed some blotchy white spots, shaped like hives, on my arms (which are the most tan part of me) and as I've gotten darker they have not. It looks like I have some scary disease with these white blotches on my arms, and I don't know what causes it. My dad claims he used to get the same thing and it just has to do with pigmentation, but I get tan every summer and have never had any problem with this before. I don't have the money or think it's serious enough to go to a dermatologist, so does anyone know what could be causing it?

2 weeks ago
The bug bite thing is a good theory, if true, since I spent 8 months of the last year in central america and was absolutely ridden with them. They are, however, not round.

probably old bug bite scars. they don't tan. maybe you were spattered with sun tan lotion, and those spots haven't caught up yet.