I started drinking a lot of milk when I tried to gain muscle. It worsened my acne by a lot so cutting dairy is a way to go. But recently I have found out that I am gluten intolerant and when you eat gluten but your body fights it your ability to digest lactose decreases too. So if not eating dairy improves your acne I'd recommend avoiding gluten too as not eating it cleared my acne completely. It is said that once your gastrointestinal tract heals you can start eating dairy again but I don't think I am there yet.