Acne is a skin problem that starts when oil and dead skin cells clog your pores. If germs get into the pores, swelling, redness and puss can result. Having a few pimples is a mild form of acne, while severe acne can mean hundreds of pimples that can cover the face, neck, chest and back. Acne is most common during adolescence because of hormonal changes that make the skin more oily after puberty. If one of your parents had severe acne, you are more likely to have it. Acne is made worse by using oily skin products that clog your pores.
Attribution: Straight Talk Foundation