OK so I have dark undereye circles do to my allergies and I do wear concelear and makeup, which covers it up fine and blends into my face but if I ever take a picture with a flash, it looks like I'm wearing a white mask around my eyes... why is that?? And how can I make it stop?

Avoid using green, white, or pink base concealers. Try using a yellow-based concealer, it corrects most dark circles.