"Dairy is such a trigger for skin problems such as acne," said Dr. Lipman. "All dairy, even if from grass-fed organic cows, comes from lactating cows. It’s therefore full of hormones from the cow, which can translate into hormonal acne in humans — particularly because it boosts male hormones, which are linked to acne. A 2009 review of 21 studies, for example, found that cow’s milk increased both the number of people who got acne and its severity."