Why does skin break out?

It's a complex issue, and even the experts don't always agree. Problem skin may derive from diet, lifestyle, exercise, environmental toxins, stress, or shampoo and make-up allergies. One article from the Food and Drug Administration claims that 85% of the U.S. population between ages 12 and 25 experiences some kind of skin trouble, and heredity appears to play a big role. But the truth is, nobody knows for sure.