myth: milk causes acne
Busted: This is another misinterpretation: milk doesn’t trigger acne or breakouts. It’s the hormones produced by cows that are found in milk that can actually overstimulate oil glands and cause overproduction of oil. As cows that give milk are pregnant most of their lives, the natural hormones that occur during pregnancy are found in the milk you drink. The reason that milk products cause acne is because milk contains hormones that "turn on" oil glands.
It is not yet known if hormones injected into cows cause any difference in the level of natural hormones in milk.