i have been wondering about this too. after massive whey, egg, and nut consumption over the course of over a decade, i started developing bad acne on my forehead all of a sudden for the first time in my life. and i'm in my 30's?!?
i have cut these things out, and the acne has largely subsided. tough to do though, as these were some of my favorites. i think bad skin is a sign of food intolerances, though it is difficult to get the close-minded medical community to give you the right kind of tests (igg) to assess these kind of things.