I have recently have been asking this myself.. There is the myth that its because when you get really excited, and dont take out that sexual tension, pimples come out(that thats why teenagers are the people that mostly have them), there is the hormonal change, and the its what you eat that gives you pimples theory.. So, which is it? I am 20 years old, and when i was about 14-18 I never had a pimple problem, but now at this age im getting more than when I was in my fifteens