Most people are Lactose intolerant to some point.. In fact, when you think about it, it's kinda hard to believe that we drink milk from another species.. even after we're no longer infants.. I stopped drinking milk ages ago. You can get calcium from countless of other stuff as well.
Besides, the milk they sell in stores are pretty bad for you.. Pasturized milk is seriously unhealthy since heating up the milk removes all the good bacterias that are supposed to make the milk way easier to digest(one of the reasons people get acne or are just lactose intolerant) to milk.
Fermented Milk as in Kefir milk or yogurt (made from raw milk that didn't go through pasteurization) is healthy since there are active bacterias that eats up the lactose which makes it drinkable. http://www.thelovevitamin.com/2810/dairy-acne/
<-- Read this if you want to learn more about dairy and acne.
Hope i helped!
Also.. As for why you get acne.. Overloaded toxins in your body and unbalanced hormones. Fuck what other people say about washing your face. If you're like me or if you still get acne then you know that washing your face isn't working (I stopped washing my face ages ago) 99% of your acne comes from within. And washing your face twice a day is just irritating.
To make things short.. Stop eating processed/refined food.. They contain all kinds of chemicals.. Stop drink pasteurized dairy, stop eat gluten, soy. COntrol your intake of sugar since it spikes your insulin levels..
You should instead eat whole foods! Drink only water, eat vegetables, fruits, make salads, make foods from the scratch! Sleep 8 hours.. least. Get some sunshine, take some cod liver oil.. Just live a healthy lifestyle. And really fuck dermatologists.. When I went to one they wanted to prescribe accutane right away.. I was like.. Yeah.. No. Accutane is poison.