POV: It's a hot, summer day and you're enjoying it by laying out. So, just as you normally would, you re-apply your sunscreen to make sure you're looking out for your skin in the midst of high UV rays. But a couple minutes later, you catch a glimpse of yourself and realize your face looks like it's covered in white paint—that's called a white cast, and yes... it's extremely annoying. Why does SPF always seem to leave a white cast?