What causes pimples and how do I stop them? Already past my teen years.

Acne causes. Acne can be from hormonal changes, stress, friction with hats, etc as well as some diets high in refined sugars and dairy. First make sure you are on good skin care products with an Alpha hydroxy, salicyclic acid and retin-a; consider peels or lasers to help prevent further damage; and if that does not work you need to have your hormones checked to rule out hormonal imbalances.